Martin Buchholz <martin(a)xemacs.org&gt; writes: However I am fairly certain this our old friend start_end_of_last_line and in that case their should have been an "assert failed" message. At first I thought it needed int pixpos = -WINDOW_TEXT_TOP_CLIP(w); just like point_would_be_visible. Although that might still be the case, it cannot fix your problem because it hits the assert before pixpos is used. The line start cache is extremely fragile. It might be that the gutter/topclip code changes its assumptions. Basically the idea here that there is a window that cannot display even a single line. This might be related to the "gutters get counted as part of the window" issue that confuses ispell. Were you running with gutters enabled? Jan