I just checked in a minor bug fix / cleanup.
The bug: boolean options/flags were being treated inconsistently. If you specified -gen=0, that meant (and still means) "do not generate." But specifying -testnet=0 did the opposite of what you might expect.
Now all boolean flags behave the same way; for example:
-gen : means generate
-gen=1 (or gen=1 in bitcoin.conf): means generate
-gen=0 (or gen=0 in bitcoin.conf): means do not generate
... and if you don't specify the option at all, that means "don't."
Check your bitcoin.conf file! If you are using anything beside "0" and "1" for boolean options, you need to change. I had:
rpcssl=true # THIS IS WRONG!
... in one of my bitcoin.conf files. The correct syntax is rpcssl=1
