Try this. Expand minibuffer so that it is a few lines long. Execute (signal-error 'error (make-list 1000 t)) For me, the list of t's is printed into the minibuffer as if it was a plain old 1200 baud terminal, then XEmacs stalls for ~3 sec, with GC cursor(?) flashing every second, 3-4 times. Increasing the length from 1000 to 1500 makes this happen 6-8 times. The relation seems to be quadratic or worse. (message "%s" (make-list 10000 t)) works flawlessly. I'll look into this, but if somebody sees something obvious... Big K