Deleting the contents of the TEMP folder shouldn't affect any web sites. I do this quite regularly and I use Ebay almost every day. I'm assuming of course that you've tried that "fix all" solution of restarting your PC since then!
You might want to try pressing [SHIFT] + [F5] to reload the Ebay pages from the Internet rather than using your local cached copies of the web page(s). On that subject, it would also be worth going into Control Panel > Internet Options and deleting your Temporary Internet Files if that hasn't helped.
Let us know how you get on