if you saved your SHSH Blobs Downgrade to an Earlier Firmware
Have you tried booting using Redsn0w? Start Redsn0w with the iPhone off, check "Just boot tethered right now", and follow the prompts.
If that doesn't work, have you tried a full restore? Are there any errors when you do that?
I had this same issue a couple days ago. Try following this guide. Apparently that's worked for a lot of people.
If that doesn't work, try restoring on another PC. That's what I ended up doing, and everything went fine.