UAC crashing explorer.exe

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I got this 2-3 month old Lenovo laptop, win 7 x64 home premium. I log in as standard user. i have UAC set to Do not Dim. maybe 60% of the time after UAC prompt pops up and I enter password to allow, explorer.exe would crash.

I did Memtest86+ for about 4 passes , nothing came up. I did sfc /scannow , nothing came up.
I did clean boot, which avast AV and 2 lenovo process still ran, crashing still happens. I also used ShellExView to disable all shell extensions in normal boot, doesnt help.

I attached a dump that I did using task manager->right click explorer.exe->Create Dump File-> !analyze -v using winDbg.

 

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i have attached my SF_Diagnostic_Tool stuff. I cant seem to get a local dump to work when explorer crashes, i attached the registry key i have seen on the threads too.

zip password is my user name.

 

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event viewer tells me it's cross-thread deadlock ..