Latest CVS broken

I'm running using today's code from CVS and can reliably get: Fatal error: assertion failed, file /export/home/georgn/src/xemacs-21.2/src/lisp.h, line 589, RECORD_TYPEP (obj, lrecord_type_cons) by simply pressing and releasing mouse 3, moving mouse outside the popped up menu and pressing mouse 1. On a different subject, did somebody make some changes around buffer stacking order? I notice now that C-x b will occassionally present me with a default that is not the last buffer I was at but rather a buffer of the same type(?). This is most irritating because I now have a *reportmail* buffer occassionally being raised in the stacking order. Was this change customizable?