THe link takes you to something posted a while ago. EBay are using some sort of system that 'logs' what PCs you access you account from. The idea is once it builds up some sort of picture it will then be able to spot the 'rogue' trying to log in.
I'd say it is too early days yet for that to be the issue, but it most likely is related to cookies.
-------------------- I loved my grandmother very much.......and she fetched a good price on eBay.