Hello, I just joined the E-junkie team to take on the brunt of support workload, and we also added another developer (very talented guy, BTW) so we'll be better able to catch up with the backlog of support requests and also improve E-junkie's performance and behaviour as well. Our apologies for being a bit absent in recent weeks as Robin was hiring and preparing for new staff on top of his previous, already-overwhelming workload -- there's only so many torches and chainsaws one man could juggle without dropping one occasionally!
BTW, something else I noticed while the cart is "stuck" in FF -- if I click on any other page tabs, the clicks don't register and switch me to those pages right away, but if I switch to a different program window (in XP) entirely, then switch back to FF, the cart screen finally disappears and all those tab clicks "catch up" to what I had clicked before, rapidfire in order. Seems something is somehow suspending the browser from responding to any click inputs at all (such as closing the cart overlay, but I can apparently check items to remove and Update Cart, hmm...) -- may be something that's happening even before the cart displays, right after clicking an item to add to the cart?
All this is not terribly specific advice, I know, but might get you looking in the right direction!