redisplay crash o' the day

this one is not the one i've recently been hitting, although i've seen this before. symptoms are that the display starts getting fucked up -- lines start appearing blank that shouldn't be. when i moved the cursor into the wrongly blank area, poof! assert_failed(const char * 0x0142f798, int 377, const char * 0x0142f790) line 3536 get_cursor_size_and_location(window * 0x044ac028, display_block * 0x04511a90, int 1, int * 0x0082fb90, int * 0x0082fba4, int * 0x0082fb80) line 377 + 20 bytes output_display_line(window * 0x044ac028, display_line_dynarr * 0x044b8310, display_line_dynarr * 0x044b8358, int 45, int -1, int -1) line 626 + 32 bytes redisplay_output_window(window * 0x044ac028) line 2287 + 25 bytes redisplay_window(long 72007720, int 0) line 6209 + 9 bytes redisplay_frame(frame * 0x04466b90, int 1) line 6434 + 17 bytes redisplay_device(device * 0x021a3cf8, int 1) line 6510 + 11 bytes redisplay_without_hooks() line 6597 + 11 bytes redisplay() line 6660 Fnext_event(long 69700124, long 21890032) line 2255 Fcommand_loop_1() line 575 + 15 bytes command_loop_1(long 21890032) line 497 condition_case_1(long 21887104, long (long)* 0x0107af49 command_loop_1(long), long 21890032, long (long, long)* 0x0107a89c cmd_error(long, long), long 21890032) line 1701 + 7 bytes command_loop_3() line 258 + 35 bytes command_loop_2(long 21890032) line 271 internal_catch(long 21662560, long (long)* 0x0107a9ec command_loop_2(long), long 21890032, int * volatile 0x00000000) line 1326 + 7 bytes initial_command_loop(long 21890032) line 307 + 25 bytes STACK_TRACE_EYE_CATCHER(int 1, char * * 0x00e52610, char * * 0x00e52c20, int 0) line 2314 main(int 1, char * * 0x00e52610, char * * 0x00e52c20) line 2690 mainCRTStartup() line 338 + 17 bytes KERNEL32! 77e8d326()