I may have done this as well... can someone explain to me how to get the sending address, or point me to a thread??

I am looking at the blockchain.info on my TX, but see plenty of addresses, and none saying 'sending address'... I just used an address I knew I could sign with.
I had trouble with this at first as well, this should help:
--snip image--
If you see multiple sending addresses on the left, choose the one in the same row as the amount you sent on the right
Interesting... yes, I do see multiple on the left, each one with a different amount of BTC (when viewing in 'advanced' mode)... I may have to wait until I get home, so I can actually see the multiple addresses I have on my client. I assume I should be able to match up one of these addresses with an address I see on my bitcoin client/wallet?