Can't clear cache/factory reset
So my phone had CyanogenMod 7.1 for awhile but it was acting pretty squirrely so I decided to flash back to stock. I SBF'ed to 4.5.608, which I found on RootzWiki, using RSDLite (I can't find a copy of the old SBF file, sadly). Seemed to work fine... except now I'm stuck in a boot loop and I need to wipe cache/clear data. I boot up and hold down the Up key and I get the triangle with the exclamation point... except then my search key does nothing. It just sits there.
So... am I pretty much screwed now? Maybe try a previous SBF? But even another SBF isn't going to let me clear the cache. Is there any other way? It's just like my search key doesn't seem to work at all. Or recovery mode isn't working. Either way.