From both of your crash dumps: two different bugchecks, but the same cause.
Code:
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* *
* Bugcheck Analysis *
* *
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Use !analyze -v to get detailed debugging information.
BugCheck C2, {99, fffffa8008207620, 0, 0}
Probably caused by : dxgmms1.sys ( dxgmms1!VIDMM_GLOBAL::CloseOneAllocation+264 )
Followup: MachineOwner
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* *
* Bugcheck Analysis *
* *
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Use !analyze -v to get detailed debugging information.
BugCheck 1000007E, {ffffffffc0000005, fffff88003756008, fffff88003316698, fffff88003315ef0}
Probably caused by : dxgmms1.sys ( dxgmms1!VIDMM_GLOBAL::ReferenceAllocationForSubmission+b8 )
Followup: MachineOwner
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So it something related with graphics. And, the dersion of the display driver you are using ATM is known to be buggy.
Code:
fffff880`048f3000 fffff880`05391000 nvlddmkm T (no symbols)
Loaded symbol image file: nvlddmkm.sys
Image path: \SystemRoot\system32\DRIVERS\nvlddmkm.sys
Image name: nvlddmkm.sys
Timestamp: Sat Dec 29 12:17:52 2012 (50DE9218)
CheckSum: 00A7F96C
ImageSize: 00A9E000
Translations: 0000.04b0 0000.04e4 0409.04b0 0409.04e4
Roll it back to an earlier stable one.
Let us know the results.