Jonathan,
very interesting. My previous test, where
set lock [ns_mutex create]
ns_mutex lock $lock
ns_mutex destroy $lock
worked fine, was on Solaris (SunOS 5.8). I just tried it again on
Linux (2.4.18, Debian 3.0), and there it crashes AOLserver every time,
with the same error message you gave.
So it seems at least on Linux, there is currently no
guaranteed safe, correct way to destroy a ns_mutex from Tcl. Not
good...