Thanks, I'll take a look later.
What's the process of fixing such things? If I happen to be able to fix this, send a patch to this list?
Yes, send a patch to the list and if the developers (who know the code better than the general user community) accept it, they will commit the change to the CVS repository and announce the change in a Daily Changelog Diff email message to the list.
Regarding your problem with menus, I have not seen this problem. I am not using CMUCL, but it sounds as though it should be independent of the Lisp used. I think that what Stas Boukarev is suggesting is that you attempt to reproduce the problem using non-compiled .el files, that is, delete your .elc files and restart Emacs.
Another step that you might try would be to minimize your SLIME configuration and attempt to reproduce the problem. For example, put your SLIME initialization code in a separate file, say, ~/.emacs.d/your-slime-init.el, and then start Emacs with:
emacs -Q --load ~/.emacs.d/your-slime-init.el
If the problem is still occurring then mail a copy of your initialization code to this list. It should then be reproducible by other SLIME users.