I bought this 3000 recently (a few months ago, maybe) and I've been using it to just play psp games on and I hadn't really thought about downgrading until now.
I've found the problem after a few months because I didn't really think much of it. The IDStorage is messed up because I had downgraded before and didn't make a nand backup. I don't think there is a fix to the IDStorage on a 3000 so I guess I'll have to stay on 6.61 :/