Unfortunately I think the only known option is the caveman one. One trick that I'll provide though is to get your hands on another sd card before doing the reset. That way after beating your phone with the caveman club you'll still have all of your data by putting the card back in the phone.
Unfortunately jasnmar is correct, you will have to do a reset of the phone. Luckily, once you get Froyo on your phone, all your apps (both purchased and free) will automatically re-install themselves for you.
How do I do a hard reboot if I cannot get to the menu? My phone is stuck on the screen asking for my Google account iD and password, which it won't accept.
I'd recommend getting an additional memory card before starting this, but it isn't a requirement.
Power off the phone.
Open the keyboard.
Press the x key.
While pressing x push the power button to turn on the phone.
Keep pressing x.
Once the "yield" sing appears release x.
Press volume up, and while holding this depress the camera key half way.
A menu will appear. You can release the two keys.
Using the dpad scroll down to "clear data / factory reset" and press the dpad button to select it.
When done, if prompted elect to restart.