"sendtoaddress" is getting the internal error 500 also. Address is valid, and I can send to it from the GUI. The address is an address on a secondary account in my wallet. Really wondering now why I can't send bit coins. The the transaction that I received did have over 500 confirmations. Anyone?
edit:
Something is really weird in Bitcoin. It appears that some JSON-RPC functions only work if the word "params" in the json begins with a capital P (ie "Params"). The "SendToAddress" and "SendFrom" only work if the word params starts with an lowercase "p" ie, "params". This is strange. I've seen a few others complaining about "some functions work and some don't", and they were using the windows client like I. Maybe it's compiled incorrectly.