That sux.. There is always one person in a pack that just HAS to complain about something even if it is their fault.. Everyone here that knows you would know for a fact that you would do anything to satisfy a customer and make sure they are happy, so they guy obviously doesn't know what he's talking about..

Just document everything that's happening and make whatever notes you can, and if you can sort it out with e-bay support and the customer (eventually), you may be able to get the negative comment wiped, or if you can REALLY sort it out with the customer, he may be able to at least write a positive comment that goes against his negative..

If none of that works though, I for one when i'm shopping on e-bay take someone with a record of 100 good to 1 bad as that person has had 100 good customers and 1 asshole...

Good luck with it..

oh yeah, what do you sell on e-bay by the way? Very cool, i'm looking at setting up something in the future also.