When I tried to run (ltktest) SBCL became unhappy: Couldn't write to #<SB-SYS:FD-STREAM for "descriptor 6" {B98E79}>: Broken pipe.
As a wild guess, maybe sbcl is having trouble connecting to the Tk command shell (wish)? Try setting *debug-tk* true before running the example. That may produce some useful output that you could send to this list.
- Daniel