It's pretty obvious you're only listing in one category so that's obviously not the problem.

You could always try auctions with make an offer, and maybe even say in the description what price you've got it set up to auto accept. That's a pretty messy solution but it may be less painful than having to ring ebay every month.

It'd be a shame to have to use a new ID to sell when you're already an established seller.

Have you tried clearing cookes and cache, just in case it makes a difference?

You could try clicking on the "number used" in your promo counter to see whether it's showing any item numbers that are supposedly already listed. If there's anything showing there it might at least help ebay to get to the bottom of things (assuming they actually try).