I have the same thing.
Only, I know where the problem lies.
It has to do with a crappy program called GameGuard from nProtect. (Look up on google)
It stops decoding files when it's running....
So now I have about 30 100mb files thats stuck on decoding. All I can do is throw them out of the list and re-download them and let them decode again.
I wish there was a altbinz.exe -command to decode where it left off or something
Now I wanted to post a request, but I can't since I'm not a donator, which is fair.
So I'll just say it here.
I want to be able to download while I play games. But decoding asks CPU and HDD time.
Why not a function to disable/enable it, simply like the auto unrar function?