Cancel/post scans seem to get stuck on some items, and every time this happens I'm able to drill down into the item after it get's past it and I find that one of the names in the Seller column is simply '?'.
If I cross-reference the seller in question against the data available on undermine journal, I'm able to see that the seller does in fact have a name. Each time this happens, it isn't any one person or item in particular. In fact usually it's someone who I'm later able to find on another of my scanned items. For example, TSM scans Wild Jade and Netherweave Cloth in that order. Wild Jade gets stuck for 30+ seconds and after it completes I find a ? in the sellers column for that item. Checking on UMJ shows that Alex is the seller. I then go back and find that Alex's name showed up as a Netherweave Cloth seller just fine.
I just moved servers, so I feel that might have something to do with it.