Killed my lookups, too. I logged in, hit check all, and waited a few minutes to click on backlinks... it happened when I went to click on keywords. Trying to restart, it won't. It shows that it is looking up, but when you switch between keywords and backlinks or hit refresh, it is not looking up. Logging out and logging back in did not help. Closing the browser, and going back to the site showed I had 0 keywords to go, and 2 links... seems to have run, but I can't go by the date, I logged in early this AM and ran out of queries, double-checking dropouts.
Try looking up a keyword without it. Then you could at least narrow it down to your server or the keyword tracker server. I'm *guessing* it might be on your end, since I can't think of anywhere off the top of my head where XML is parsed on the keyword tracker side if you are using the advanced usage script.
Looking up individuals seemed to work. I'll go try a few now. Like I said, I think it updated, but I couldn't go by the date... it may have only done some.