Well...
I was modding someone else's PSP and I figured out the problem.
Apparently, after you run the flash builder, if there's an error it will report it on the screen, but it closes in 10 seconds. I went out for a smoke and just assumed everything went well and flashed a corrupted version to my psp. Sucks, but it happens.
I managed to get yet another PSP for $100 and got everything working OK. My advice to anyone else who may have the SHA-1 error - flash that and you'll brick.

Thanks for your help anyways, 2 psp's means it's a good idea to have a 3rd for parts and what not.