I had a same case like you. I'm using Corsair Force3 120 GB SSD. After I tried many way to solve it, finally I found only one way that WORK!!!.Try to turn off TRIM on your Windows 7 by run command prompt (cmd), then type "fsutil behavior set disabled...

I also have faced this issue until this morning, I try to disable TRIM for SSD by open cmd, then type "fsutil behavior set disabledeletenotify 1".Until now, there is no freeze any more.