Here is the result of the diagnostic running when the site crashed:
In w3wp__PID__6184__Date__03_05_2009__Time_09_39_31AM__788__Second_Chance_Exception_C0000005.dmp the assembly instruction at ntdll!RtlpCoalesceFreeBlocks+128 in C:\WINDOWS\system32\ntdll.dll from Microsoft Corporation has caused an access violation exception (0xC0000005) when trying to read from memory location 0x6ae7b3d5 on thread 8 Heap corruption was detected in heap 0x01ae0000, however pageheap was not enabled in this dump. Please follow the instructions in the recommendation section for troubleshooting heap corruption issues. Current NTGlobalFlags value: 0x0