There is a bug in the 0.3.20 candidate release that causes rendering issues on Windows.
I have no idea how to fix it; I don't even have a real Windows machine on which to test it (I built 0.3.20 on an Amazon EC2 windows virtual machine).
Anybody willing to step up and fix it?
If nobody steps up and commits to continuing to develop the wxWidgets GUI, we may have to stop supporting/developing it and start releasing only bitcoind.