redisplay crash again

i've seen this before. symptoms are weirdness in the way it displays lines, with lines blank or in the wrong places, and confusion about where the cursor is. i'm prepared to put in some work writing a sledgehammer function if someone can give me an overview of the redisplay structures, with an eye towards what should always be consistent with what. ben assert_failed(const char * 0x012be274, int 379, const char * 0x012be26c) line 3536 get_cursor_size_and_location(window * 0x02394338, display_block * 0x03efa9f0, int 22, int * 0x0082e7a0, int * 0x0082e7b4, int * 0x0082e790) line 379 + 20 bytes output_display_line(window * 0x02394338, display_line_dynarr * 0x024fbe28, display_line_dynarr * 0x03836cc0, int 32, int -1, int -1) line 628 + 32 bytes redisplay_output_window(window * 0x02394338) line 2289 + 25 bytes redisplay_window(long 37307192, int 0) line 6208 + 9 bytes redisplay_frame(frame * 0x025757c0, int 1) line 6433 + 17 bytes redisplay_device(device * 0x01fc8de8, int 1) line 6509 + 11 bytes redisplay_without_hooks() line 6596 + 11 bytes redisplay() line 6662 Fsit_for(long 1, long 20102000) line 2874 Ffuncall(int 2, long * 0x0082e9f8) line 3488 + 93 bytes execute_optimized_program(const unsigned char * 0x0247eaa8, int 4, long * 0x014693dc) line 745 + 16 bytes funcall_compiled_function(long 21572316, int 0, long * 0x0082ecd0) line 517 + 35 bytes Ffuncall(int 1, long * 0x0082eccc) line 3523 + 17 bytes execute_optimized_program(const unsigned char * 0x023e4af8, int 5, long * 0x014694b4) line 745 + 16 bytes funcall_compiled_function(long 21572400, int 0, long * 0x0082efa8) line 517 + 35 bytes Ffuncall(int 1, long * 0x0082efa4) line 3523 + 17 bytes execute_optimized_program(const unsigned char * 0x0255d1e0, int 4, long * 0x01469e64) line 745 + 16 bytes funcall_compiled_function(long 21573296, int 0, long * 0x0082f27c) line 517 + 35 bytes Ffuncall(int 1, long * 0x0082f278) line 3523 + 17 bytes execute_optimized_program(const unsigned char * 0x0255d188, int 2, long * 0x01469fe4) line 745 + 16 bytes funcall_compiled_function(long 21573436, int 2, long * 0x0082f548) line 517 + 35 bytes Ffuncall(int 3, long * 0x0082f544) line 3523 + 17 bytes execute_optimized_program(const unsigned char * 0x0253bb20, int 4, long * 0x014690dc) line 745 + 16 bytes funcall_compiled_function(long 21571868, int 1, long * 0x0082f81c) line 517 + 35 bytes Ffuncall(int 2, long * 0x0082f818) line 3523 + 17 bytes execute_optimized_program(const unsigned char * 0x0253bac8, int 2, long * 0x0146a17c) line 745 + 16 bytes funcall_compiled_function(long 21573632, int 0, long * 0x0082fb04) line 517 + 35 bytes Ffuncall(int 1, long * 0x0082fb00) line 3523 + 17 bytes apply1(long 21573632, long 20102000) line 4112 + 11 bytes Fcall_interactively(long 20027552, long 20102000, long 20102000) line 463 + 13 bytes Fcommand_execute(long 20027552, long 20102000, long 20102000) line 2929 + 17 bytes execute_command_event(command_builder * 0x01658fa0, long 37105436) line 4069 + 25 bytes Fdispatch_event(long 37105436) line 4364 + 71 bytes Fcommand_loop_1() line 585 + 9 bytes command_loop_1(long 20102000) line 498 condition_case_1(long 20099960, long (long)* 0x01064e46 command_loop_1(long), long 20102000, long (long, long)* 0x010649af cmd_error(long, long), long 20102000) line 1692 + 7 bytes command_loop_3() line 259 + 35 bytes command_loop_2(long 20102000) line 272 internal_catch(long 19872512, long (long)* 0x01064aff command_loop_2(long), long 20102000, int * volatile 0x00000000) line 1323 + 7 bytes initial_command_loop(long 20102000) line 308 + 25 bytes xemacs_21_5_b5_i586_pc_win32(int 1, char * * 0x00e52610, char * * 0x00e52ba0, int 0) line 2314 main(int 1, char * * 0x00e52610, char * * 0x00e52ba0) line 2690 mainCRTStartup() line 338 + 17 bytes KERNEL32! 77e8d326()