Just posting up the debug as requested.
Happens during analyze on IDE drive in XP SP3:
Two times so far, after 5% and 50%.
14:43:50 I have crashed in function 'DefragThread' in source '.\MyDefrag.cpp' on line 53.
Exception: ACCESS_VIOLATION (the memory could not be read or written)
Command line: "C:\Program Files\MyDefrag v4.2.6\MyDefrag.exe"
Context is not locked.
Failed to load 'dbghelp.dll':  The specified module could not be found.
Please download and install the debug version of MyDefrag from: http://www.mydefrag.com/debug.html