The attached DMP file is of the IRQL_GT_ZERO_AT_SYSTEM_SERVICE (4a) bug check.
This indicates that a thread is returning to user mode from a system call when its IRQL is still above PASSIVE_LEVEL.
Bitdefender is known to cause this bug check (0x4A), so please remove and replace BitDefender with Microsoft Security Essentials for temporary troubleshooting purposes as it's very likely causing conflicts:
BitDefender removal - http://www.bitdefender.com/support/how-to-uninstall-bitdefender-333.html
MSE - http://windows.microsoft.com/en-us/windows/security-essentials-download