I had this before a while ago, it fixed itself eventually. You can't
log in or connect but everyone else can. :-(

It could your cache. With another site I couldn't access it at the normal
address, but I got it sussed by putting "www" in the address. There are two
alternative addresses for ebay. One with and one without "www". Some sites
actually give a different page depending on whether or not you use "www"
before the address.