I've done it before. 48 hours to receive payment goes to the next highest bidder I think. I tried to get ahold of the initial winner as much as i could during that time period as well, he was on the forums a couple days ago after I announced he won and didn't do anything in regards to this auction
You are expected to pay within 48 hours of winning an auction, unless you and the auction host agree to different terms, or if the auction's OP states that there is a different time you have to pay within. That's in the Auction rules thing. I don't know how to quote it though haha.