I read in their forums that ebay is notorious for slow credits. Maybe there is still hope. Also, be sure to check your account history back on the day you did the offer, that is where it will pend....so it might be a page back or something.
As far as the stop crediting issue, did anything new go on with your computer? New program installed like virus protection, etc? Any toolbars on your browser? Switch to Vista? Do you use a new email address every so often so it is fresh in the advertisers database? Sorry, I know you didn't ask for answers here, just seemed like you liked it once so trying to help