It looks like, shortly after being moved to c-l.net, clim-gui.lisp was changed to use clim's builtin toplevel instead of CLOSURE-FRAME-TOP-LEVEL. For me, anyway, that broke startup and the quit command. The old toplevel used to set *closure-inited-p* to t and establish the 'closure-quit catch tag. So I tried doing that, and it seems to have helped.
Also, I added scroll-bars to the interactor pane. Without them the interactor will write over the "wholine" on the bottom and then stop updating. I don't know if that's something that should be fixed in mcclim, or if it's a "don't do that" kind of thing.
Lastly, I switched an MP:PROCESS-INTERRUPT to a CLIM-SYS:PROCESS-INTERRUPT, thinking that the latter would be more portable. (It's portable to SBCL anyway.)