Don't worry, pretty common happening with ebay once they have identified your listings as falling outside their advertising guidelines.
All that will happen now is that any current bidders will be notified of the cancellation, and you will not be permitted to list the items again. Your account other than that will not be effected in any way, and no refunds from past sales will be required. In fact previous customers won't even be aware of the issue unless they were a current bidder.
Just be very careful now as to what you do list, as your seller status will have taken a bit of a dent as far as ebay themselves are concerned, but nothing to be concerned about so long as you don't get caught again.