Below is an error I got when I did (asdf:oos 'asdf:load-op 'usocket) using clisp-2.43 on Windows 2000.

>>>> snip <<<<

READ from #<INPUT BUFFERED FILE-STREAM CHARACTER #P"C:\\home\\lisp\\asdf-registry\\usocket\\backend\\clisp.lisp" @203>: #1=#<PACKAGE
     RAWSOCK> has no external symbol with name "SOCKET-CLOSE"
   [Condition of type SYSTEM::SIMPLE-PACKAGE-ERROR]

Restarts:
 0: [RETRY] Retry performing #<ASDF:COMPILE-OP NIL #x19F82EF9> on #<ASDF:CL-SOURCE-FILE "clisp" #x19F82199>.
 1: [ACCEPT] Continue, treating #<ASDF:COMPILE-OP NIL #x19F82EF9> on #<ASDF:CL-SOURCE-FILE "clisp" #x19F82199> as having been successful.
 2: [ABORT] Return to SLIME's top level.
 3: [CLOSE-CONNECTION] Close SLIME connection

Backtrace:
  0: INVOKE-DEBUGGER
  1: SYSTEM::LPAR-READER
  2: SYSTEM::LPAR-READER
  3: SYSTEM::LPAR-READER
  4: SYSTEM::FEATURE-READER
  5: READ
  6: unwind-protect frame
  7: unwind-protect frame
  8: unwind-protect frame
  9: unwind-protect frame
 10: COMPILE-FILE
 11: (COMPILE-FILE ASDF:SOURCE-FILE :OUTPUT-FILE ASDF::OUTPUT-FILE)
 12: MULTIPLE-VALUE-BIND
 13: LET
 14: (:LAMBDA '#<ASDF:COMPILE-OP NIL #x19F82EF9> '#1=#<ASDF:CL-SOURCE-FILE "clisp" #x19F82199>)
 15: :LAMBDA (ASDF:OPERATION ASDF::C) (DECLARE (IGNORABLE ASDF:OPERATION ASDF::C)) (BLOCK ASDF:PERFORM (LET (# #) (MULTIPLE-VALUE-BIND # # # # #)))
 16: ((LAMBDA #1=(ASDF:OPERATION ASDF::C) (DECLARE (SYSTEM::SOURCE #)) #2=(DECLARE (IGNORABLE ASDF:OPERATION ASDF::C)) #3=(LET (# #) (MULTIPLE-VALUE-BIND # # # # #))) #:G4057 #:G4058)
 17: frame binding functions #<ADDRESS #x011218B0> binds (~ = dynamically):
       |  CALL-NEXT-METHOD <--> #<FUNCTION-MACRO #<FUNCTION CALL-NEXT-METHOD (SYSTEM::<MACRO-FORM> SYSTEM::<ENV-ARG>) (DECLARE (CONS SYSTEM::<MACRO-FORM>)) (DECLARE (IGNORE SYSTEM::<ENV-ARG>)) (IF (NOT #) (SYSTEM::MACRO-CALL-ERROR SYSTEM::<MACRO-FORM>) (LET* # #))> #<FUNCTION CALL-NEXT-METHOD (&REST CLOS::NEW-ARGS) (IF CLOS::NEW-ARGS (IF # # #) (IF #:G4056 # #))>>
       Next environment:
       | NEXT-METHOD-P <--> #<FUNCTION-MACRO #<FUNCTION NEXT-METHOD-P (SYSTEM::<MACRO-FORM> SYSTEM::<ENV-ARG>) (DECLARE (CONS SYSTEM::<MACRO-FORM>)) (DECLARE (IGNORE SYSTEM::<ENV-ARG>)) (IF (NOT #) (SYSTEM::MACRO-CALL-ERROR SYSTEM::<MACRO-FORM>) (LET* NIL #))> #<FUNCTION NEXT-METHOD-P NIL #:G4056>>
       | CALL-NEXT-METHOD <--> #<FUNCTION-MACRO #<FUNCTION CALL-NEXT-METHOD (SYSTEM::<MACRO-FORM> SYSTEM::<ENV-ARG>) (DECLARE (CONS SYSTEM::<MACRO-FORM>)) (DECLARE (IGNORE SYSTEM::<ENV-ARG>)) (IF (NOT #) (SYSTEM::MACRO-CALL-ERROR SYSTEM::<MACRO-FORM>) (LET* # #))> #<FUNCTION CALL-NEXT-METHOD (&REST CLOS::NEW-ARGS) (IF CLOS::NEW-ARGS (IF # # #) (IF #:G4056 # #))>>
 18: SYSTEM::FUNCTION-MACRO-LET
 19: (:LAMBDA '#<COMPILED-FUNCTION #:COMPILED-FORM-322-1-1> '#<ASDF:COMPILE-OP NIL #x19F82EF9> '#1=#<ASDF:CL-SOURCE-FILE "clisp" #x19F82199>)
 20: :LAMBDA (#:G4056 #:G4057 #:G4058) (SYSTEM::FUNCTION-MACRO-LET ((CALL-NEXT-METHOD # #) (NEXT-METHOD-P # #)) ((LAMBDA # # #) #:G4057 #:G4058))
 21: #:COMPILED-FORM-322-1
 22: (ASDF:PERFORM ASDF::OP ASDF:COMPONENT)
 23: PROGN
 24: RETURN-FROM
 25: LET*
 26: nested tagbody frame #<ADDRESS #x011217B0> for
       | #:G4154 --> ((RETURN-FROM #:RESTART-4155 (APPLY #'(LAMBDA NIL # # #) #:ARGS-4156)))
       | #:G4153 --> ((RETURN-FROM #1=#:RESTART-4155 (APPLY #'(LAMBDA NIL #) #2=#:ARGS-4156)) #:G4154 (RETURN-FROM #1# (APPLY #'(LAMBDA NIL # # #) #2#)))
       Next environment:
       | #(#:G4154 #:G4153) --> #<ADDRESS #x011217B0>
       | #(#:LOOP-4152) --> #<ADDRESS #x01121724>
       | #(SYSTEM::END-LOOP SYSTEM::BEGIN-LOOP) --> #<ADDRESS #x011216D0>
 27: TAGBODY
 28: LET
 29: nested block frame #<ADDRESS #x01121744> for #:RESTART-4155
       Next environment:
       | #:RESTART-4155 --> #<ADDRESS #x01121744>
       | NIL --> #<ADDRESS #x011216F0>
 30: BLOCK
 31: nested tagbody frame #<ADDRESS #x01121724> for
       | #:LOOP-4152 --> ((BLOCK #1=#:RESTART-4155 (LET (#2=#:ARGS-4156) (TAGBODY # #3=#:G4153 # #4=#:G4154 #))) (GO #:LOOP-4152))
       Next environment:
       | #(#:LOOP-4152) --> #<ADDRESS #x01121724>
       | #(SYSTEM::END-LOOP SYSTEM::BEGIN-LOOP) --> #<ADDRESS #x011216D0>
 32: TAGBODY
 33: nested block frame #<ADDRESS #x011216F0> for NIL
       Next environment:
       | NIL --> #<ADDRESS #x011216F0>
 34: BLOCK
 35: nested tagbody frame #<ADDRESS #x011216D0> for
       | SYSTEM::END-LOOP --> NIL
       | SYSTEM::BEGIN-LOOP --> ((WHEN (ENDP #1=#:LIST-4150) (GO SYSTEM::END-LOOP)) (SETQ ASDF::OP (CAR (SETQ #2=#:PATTERN-4151 #)) ASDF:COMPONENT (CDR #2#)) (BLOCK NIL (TAGBODY #3=#:LOOP-4152 (BLOCK #4=#:RESTART-4155 #) (GO #3#))) (PSETQ #1# (CDR #1#)) (GO SYSTEM::BEGIN-LOOP) SYSTEM::END-LOOP)
       Next environment:
       | #(SYSTEM::END-LOOP SYSTEM::BEGIN-LOOP) --> #<ADDRESS #x011216D0>
 36: TAGBODY
 37: LET
 38: LET
 39: LET
 40: LET
 41: unwind-protect frame
 42: UNWIND-PROTECT
 43: PROGV
 44: LET
 45: LET
 46: LET*
 47: (ASDF:OPERATE 'ASDF:LOAD-OP 'USOCKET)
 48: ASDF:OPERATE (ASDF::OPERATION-CLASS ASDF:SYSTEM &REST ASDF::ARGS &KEY (ASDF::VERBOSE T) ...) (DECLARE (SYSTEM::IN-DEFUN ASDF:OPERATE)) (BLOCK ASDF:OPERATE (LET* (# # #) (UNLESS # #) (LET # #)))
 49: (ASDF:OPERATE 'ASDF:LOAD-OP LIB)
 50: (ASDF 'USOCKET)
 51: ASDF (LIB) (DECLARE (SYSTEM::IN-DEFUN ASDF)) (BLOCK ASDF (ASDF:OPERATE 'ASDF:LOAD-OP LIB))
 52: (ASDF 'USOCKET)
 53: EVAL
 54: unwind-protect frame
 55: SWANK::EVAL-REGION
 56: SWANK::REPL-EVAL-1-1
 57: unwind-protect frame
 58: SWANK::TRACK-PACKAGE
 59: SWANK::REPL-EVAL-1
 60: #:|314 316 (DEFINTERFACE CALL-WITH-SYNTAX-HOOKS (FN) ...)-32-3-1|
 61: SWANK-BACKEND:CALL-WITH-SYNTAX-HOOKS
 62: SWANK::CALL-WITH-BUFFER-SYNTAX
 63: SWANK::REPL-EVAL
 64: SWANK:LISTENER-EVAL
 65: (SWANK:LISTENER-EVAL "(asdf 'usocket)
     ")
 66: EVAL
 67: unwind-protect frame
 68: SWANK::EVAL-FOR-EMACS-1
 69: #:|588 593 (DEFINTERFACE CALL-WITH-DEBUGGER-HOOK (HOOK FUN) ...)-57-3-1|
 70: SWANK-BACKEND:CALL-WITH-DEBUGGER-HOOK
 71: SWANK::EVAL-FOR-EMACS
 72: SWANK::READ-FROM-EMACS
 73: catch frame for tag #:SIMPLE-RESTART-22247
 74: SWANK::HANDLE-REQUEST-1
 75: #:|588 593 (DEFINTERFACE CALL-WITH-DEBUGGER-HOOK (HOOK FUN) ...)-57-3-1|
 76: SWANK-BACKEND:CALL-WITH-DEBUGGER-HOOK
 77: SWANK::CALL-WITH-CONNECTION-1
 78: SWANK::CALL-WITH-REDIRECTED-IO
 79: SWANK::MAYBE-CALL-WITH-IO-REDIRECTION
 80: SWANK::CALL-WITH-CONNECTION
 81: SWANK::HANDLE-REQUEST
 82: SWANK::SIMPLE-SERVE-REQUESTS-2
 83: handler frame for conditions SWANK::SWANK-ERROR
 84: compiled block frame for #S(RESTART :NAME SWANK::CLOSE-CONNECTION :TEST #<COMPILED-FUNCTION SYSTEM::DEFAULT-RESTART-TEST> :INVOKE-TAG #:SIMPLE-RESTART-22757 :INVOKE-FUNCTION NIL :REPORT #<FUNCTION :LAMBDA (STREAM) (FORMAT STREAM "Close SLIME connection")> :INTERACTIVE #<COMPILED-FUNCTION SYSTEM::DEFAULT-RESTART-INTERACTIVE> :MEANINGFULP T)
 85: catch frame for tag #:SIMPLE-RESTART-22757
 86: unwind-protect frame
 87: SWANK::SIMPLE-SERVE-REQUESTS
 88: SWANK::SERVE-REQUESTS
 89: unwind-protect frame
 90: SWANK::SERVE-CONNECTION
 91: SWANK::SETUP-SERVER-SERVE
 92: SWANK::SETUP-SERVER
 93: SWANK:START-SERVER
 94: (FUNCALL (READ-FROM-STRING "swank:start-server") "c:/DOCUME~1/102508/LOCALS~1/Temp/slime.2292" :CODING-SYSTEM "iso-latin-1-unix")
 95: PROGN
 96: SYSTEM::READ-EVAL-PRINT
 97: compiled tagbody frame for #(NIL)
 98: catch frame for tag DEBUG