Have you tried talking to livehelp?
https://cschatlb-na.corp.ebay.com/ch...tionInactiveHP
I don't know if they will speak to you or not, seeing as you are naru.
But if it's worth your while (and by the sounds of it, it is) then a solicitors letter makes ebay jump through hoops.
You can put money on the fact that someone had grassed you up for trading again...ebay don't put two and two together very often.
You'll probably find that your rival saw you were trading again and told ebay that you were already naru on the other account.