I will fix it asap, thank you. We missed it probably in the last API changes.
EDIT: What game is it?
As I recall, it happens on every game. Most recent example (that may be still in the log file) is with The Witcher 2. Queued both Mac and Win installers, paused and moved them around a bit when it would pause at the last segments, closed downloader, restarted it, only one installer in the queue. Re-adding the other installer will continue the download, after the hash check.
Can do a more thorough report if you wish, though probably during the weekend.