consent.exe -- suspect, not flagged by NIS or MBAM

My new i5 Win7 system was assembled in November 2011 and has been stable since then.
Windows Security Essentials was installed and worked normally.
It has two identical HDD in RAID 0 mirror volume (intel RST systray applet), cached onto 120 GB SSD using Intel Smart Response Technology (SRT)

A few days ago, my system started having intermittent lockups and freezes.
Most commonly, the Start menu would become unresponsive – the buttons would no longer highlight under the mouse pointer, clicking produces ‘ding!’ sound.
Windows + E would produce an RPC error message
Task Manager shows multiple consent.exe threads, no accompanying confirmation dialog
When the system locks up, only a hardware reset would enable a restart.
On reset, the cache rebuilds and the system halts after the RAID BIOS screen. After a second reset, Windows loads and on login, intel RST verifies RAID data integrity. Both cache rebuild and RAID verification are successful.

I have scanned the system with Malwarebytes Anti-malware (1 trojan found and removed) and Norton Internet Security (100 tracking cookies, threat assessment: “mild”, removed). I have also run sfc /scannow in a cmd.exe window with admin privileges.

I suspect that C:\Windows\system32\consent.exe (112,000 bytes) on my system is malware: For instance, Start > All Programs > Accessories > Command Prompt (right-click) Run as administrator will start another consent.exe, the start menu stops working, and the command prompt window does not appear.

I think the genuine consent.exe is more like ~87,000 bytes, can’t remember exactly.

Any advice on how to fix this without wiping everything and starting from scratch would be greatly appreciated.

Thank You for reading! ^_^

consent.exe = UI for admin apps (UAC)

W7 x64 SP1 -

Code:

 Directory of C:\Windows\system32

11/20/2010  08:32           112,000 consent.exe
               1 File(s)        112,000 bytes