Assertion failure

I don't have any repro for this but it bites me about once a day. I don't have a core file to look at. This is happening to me on OSX with the latest hg sources. Seems to be related to something happening in the minibuffer when I'm entering something, but I'm not sure if that's really true. Fatal error: assertion failed, file /Users/rtoy/src/XEmacs/beta/xemacs/src/marker.c, line 371, byteno == old_byteno Lisp backtrace follows: # (unwind-protect ...) # (unwind-protect ...) # bind (inhibit-quit) # (unwind-protect ...) # (unwind-protect ...) # (unwind-protect ...) # (unwind-protect ...) # (unwind-protect ...) # (unwind-protect ...) # (unwind-protect ...) # (unwind-protect ...) # (unwind-protect ...) redisplay-echo-area() # bind (inhibit-read-only end start #:--rest--65942 stdout-p frame message) raw-append-message("Quit" #<x-frame "XEmacs" on #<x-device on "/private/tmp/com.apple.launchd.z7ldN3fjkF/org.macosforge.xquartz:0.0" 0x2> 0x2> nil :start 0 :end nil) # bind (end start #:--rest--65934 stdout-p frame message label) append-message(error "Quit" #<x-frame "XEmacs" on #<x-device on "/private/tmp/com.apple.launchd.z7ldN3fjkF/org.macosforge.xquartz:0.0" 0x2> 0x2> nil :start 0 :end nil) # bind (print-message-label) display-error((quit) t) # bind (etype debug-on-error inhibit-quit error-object) command-error((quit)) # (catch top-level ...) -- Ray