Am i obliged to buy when seller refused at first..

If the Seller refused your offer through the Audiogon messaging system, then later accepted your offer through the Audiogon Offer button you should send Audiogon an e-mail with all of this information, and ask them to refund the $19 and remove the negative feedback. I don't think the Seller should get two bites at the apple. They can't refuse, then accept.

Best to always ask the seller to move the transaction to eBay so you get more safety and security. Ebay works much better of buyers then sellers.

Wow, I see a lot of people don't understand how this Audiogon system works at all. I'm not saying that I agree with the system, but there is a BIG difference between refusing an offer and declining an offer.
Do some research, find out how the system works, then work the system. That is what the seller did.

As Swampwalker suggests, state your case with the documented messages and you'll at least get the neg. feedback removed.

Jmcgrogan2 has made a profound statement. This guy knows how to work the system; he's never going to get burned on a transaction.

When I read about this new rule last year I was disgusted. This decision by AgoN is very arbitrary and leaves the consumer at the mercy of someone who all s/he want is to probably unload something in a hurry. If this individual (seller) is not the understanding type you could be in for a rough ride. Instead of keeping a level playing field, AgoN has sided with the seller in this case. I have not agreed to the new rules as I refuse to give up my CC number. I still browse but I have not made any offers as I know AgoN is going to try to lock me in. It is a good thing we have a couple of options out there still.