Sounds like you've been done.
Theres a slight possibility he may have messed up his funding but id say 9/10 times you've been done here.
I always leave a few days before sending stuff as usually if they pull this stunt it will transpire in the first two days.
Here are my seller tips although it may well be too late for you, I might add I sell a lot of high value stuff:
Don't ever send to Nigeria (I don't sell out of the UK)
Don't accept western union ever
State clear your terms on your listing - dont shoot yourself in the foot
Regardless of anything, immediately withdraw the payment into your bank account, don't leave it in paypal. It may or may not have anything to do with how quick fraud is detected but i like to think that because you are performing an action on the funds, fraud may be quicker detected if the source is not legitimate.
Check to see whether the name of the ebayer buying matches that of the payer in the paypal screen. Excuses like "my mum/son/sister/dog/mongoose is paying for me" should result in you delaying postage to minimise loss risk to yourself. In your case the sender is "mhaumesser ebay" which rings alarm bells as 9/10 it should just be the name on their bank card.
Make sure their feedback is relatively good. In my opinion, anything south of 20 is suspicious. Check to see if they have bought any high value items. 20 purchases of 10p stickers looks like a blatant attempt to build feedback.
Any messages asking to send the item asap should be treated with suspicion. Yes, some people are impatient, but so are scammers.
Ebayers with very high feedback and confirmed paypal addresses are generally to be trusted unless behaving suspiciously.
If in any doubt whatsoever, delay posting of the item. I believe Ebay allows the seller a week to dispatch items, make full use of it.
My tips may be controversial to some but ebay is a dog-eat-dog world and you must look out for number one. I for one am not for losing £500 because i was concentrating on being nice to people - thats not to say you shouldnt be nice to your buyers
