Lsass.exe High Memory Usage?

I've lately been experiencing some peculiar issues with my PC - most notably, excessive usage of lsass.exe.

Starts off very low memory use - ~5mb, but steadily climbs up. It's been 4 hours since I've turned my PC on and currently, it's at 150mb usage. Last night by the end of the night it was close to 1GB.

I know all about the Sasser worm, and this is not it.

I've done all of the malware scans (Malwarebytes, Spybot, Hijack This), virus scans (ESET NOD32), etc. Nothing.

My PC stats:

Windows 7
Core i7 920
Gigabyte EX58-UD4P
6GB DDR3
3x HDD's (WD640AALS, WD1001FALS, WD20EADS)

I tend to have ~60-70 processes running at one time.. Most of which are Chrome and svchost processes. Here is a pic of my process manager that shows most of my processes. [URL]