I got a RROD 360 on craigslist.
Replaced thermal comp w/AS5.
Noticed fan wasn't even coming on when I tried to overheat it.
Swapped power supply with known working one.

Now what I'm getting is the startup animation swirly thing freezes and sometimes goes to solid green screen.

I get no red lights or error codes.
Here's a few vids for clarification:

http://youtu.be/dgxjLAv0taU
http://youtu.be/riOi9C8HeMc
http://youtu.be/i4leUcRx9NE

Fixable?

In case anyone is wondering. I did the X-Clamp fix, let it cook itself for an hour and now it seems to be working fine. Power supply is still crap though.

Your fix is temporary and most likely damaged the board even more.