I cant tell anything from the log, maybe someone else can. However it did happen to myself once... and was able to track it down. You may want to check permissions on the directory, files, and locked handles. If the 2GB was a whole download, did the directory get created as expected? What is the permissions of the parent directory? Does it happen all the time? or just that once?
In my case, i had tried to play something I had downloaded in BS player, and realized it was failed so I hit stop, forgetting to close bsplayer. One of the failed files happened to be the .rar file. When I re-downloaded it, it got to the decoding stage, sat on 99% and would not complete. I then realized I had bsplayer running still and closed it, giving altbinz a few minutes to retry. It never did, so I deleted the file from the queue and repaired it from pars.
This should probably be fixed by a popup with retry/cancel. "File locked, fix the problem and retry." This should of course be done in a way that it does not interfere with background tasks.