Few things to check: first of all, what does your (detailed) log report?
Secondly, can you see a timer icon next to the files in the queue? This means that Alt.binz couldn't find the articles and is waiting to retry the server - check your settings in Setup > Connection > 'Article not found' etc. Check also whether there are waiting article parts in your temp folder. If you can actually see the 'Decoding xx%' message in the queue, then it's another issue.
Thirdly, some users have reported decoding problems with certain anti-virus programs. Make sure your temp and downloaded folders are excluded from scanning.
Finally, restarting Alt.binz can help to shift things, depending on your issue. And there are some other solutions, but try these first.
-Hecks