Dumps attached per discussion
HERE. (Note, these are two new dumps, one from the shell process and the other from a seperate file manager explorer.exe process) - yes I tell explorer to start a new process when starting the file manager, etc.
Excellent write-up. Have rep :)
All 3 of these dumps show a situation called "heap corruption", although the first one is subtly different. "Heap" can be thought of as a region of memory within the process which is allocated to parts of the process as they ask for memory. They must not write over each other's allocations, and it is up to each "part" to ensure that it stays within the confines of what it has allocated for itself.
There are ways to enable special diagnostic heap behaviour, so that the OS pays more attention to who's doing what with heap - at the expense of somewhat degraded performance. That way you can sometimes catch the heap corruptor component in the act, rather than simply witnessing the aftermath later when the corrupted memory is used.
Before we get too carried away, could you please consider temporarily uninstalling 7zip and AVG in order to get rid of their Explorer integration componentry as a test:
Image path: C:\Program Files\7-Zip\7-zip.dll
Image name: 7-zip.dll
Timestamp: Sat Aug 29 20:39:40 2009 (4A99056C)
...
Image path: C:\Program Files (x86)\AVG\AVG8\avgsea.dll
Image name: avgsea.dll
Timestamp: Wed Jul 08 10:22:16 2009 (4A53E6B8)
After that, if the crashes continue, we may need to tweak some settings before generating more dumps.
(BTW, I and others may also be able to help with your MMC crash, but I'd suggest another separate thread for that. The way to get dumps will be a bit different since the process, as I understand it, crashes on startup.)