When this happened to me I emailed them at around midnight and by 2 am they had closed all the listings down that I had, had a top service from em.

I was allegedly selling over 300 mobile phones on a 1 day listing.... marvellous.

You must have replied to an email at some point which has allowed them to hack your account. The trick is, never to reply to any questions or mails, UNLESS they are actually in your e-bay Messages list.