This happens to me on my ADFII with the IQ180 all the time. Taking the back off the camera and then replacing the battery with a different one seems to resolve it. Pulling out and reinserting the same battery does not resolve it for me (maybe leaving it out for a while would work). Once the back gets in this condition, it will not work (take an exposure) even on a tech camera until the battery is replaced. Always having the back on when turning on or off the camera seems to help avoid the problem. The first time this happened it was very inconvenient, but 15 minutes of try this and try that, I figured it out. If you put the back on the camera, and the mirror doesn't click closed, then you know you've got the problem. My firmware version is 1.34 (from factory) which is one higher than what is available from the P1 website (1.33), not sure what that means if anything.
BTW, aren't we over due on a firmware update? I need tethered camera control and capture pilot. And would like to try composition mode on tech camera (for adjusting exposure and WB and not consuming an exposure that I have to then delete). Maybe I shouldn't assume, will you be able to set WB in composition mode?