With regards to your edit, and not being able to set a fee, there's a known bug that results in something similar which has been discussed in the past. [Here for Mac, here for other platforms. I've hit the problem myself.]

If you're hitting this bug and your wallet isn't being kept in sync, then perhaps the same IPC issue is causing problems with interacting with the etherbase account.

See the previous threads for suggestions on how to fix it, but I think it basically comes down to finding a version of Geth and Mist that work together...