All of the crashes were triggered by the same driver.
Could not read faulting driver name
Probably caused by : aswSnx.SYS ( aswSnx+42b31 )
According to this page it's a component of Avast! and the timestamp seems rather old.
0: kd> lmDvm aswSnx
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start end module name
fffff880`0433e000 fffff880`043b5000 aswSnx T (no symbols)
Loaded symbol image file: aswSnx.SYS
Image path: \SystemRoot\System32\Drivers\aswSnx.SYS
Image name: aswSnx.SYS
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Timestamp: Tue Sep 7 07:54:08 2010 (4C865210)
Translations: 0000.04b0 0000.04e4 0409.04b0 0409.04e4
Information from resource tables:
I'd suggest checking for an update to Avast! or uninstalling Avast! and using Microsoft Security Essentials instead; at least while troubleshooting. It's strange that it happens intermittently but perhaps it's caused by a race condition. Depending on the age of the system drive I'd also consider it a possibility the drive is having issues.