Whenever I add one or more new torrents which are bigger than 1 GB, after a download speed spike, this happens:

http://img4.imageshack.us/img4/636/49254389.png

The download speed just stalls like that for up to 5 minutes, and the message Disk overloaded 100% is shown. Stopping all the other torrents doesn't help. After that time the download(s) resume(s) normally. Why is this happening?

I can't tell, but maybe you are saving your files to an external hard drive or something (or even an internal hard drive for that matter)? Sometimes those external hard drives are pre-formatted as FAT instead of NTFS. If the drive is formatted as FAT then there is a file size limit of something in the few GB range (I think it is just shy of 3 GB). If you are downloading files larger than 3GB then you would probably get some strange errors when your client tries to put them on the FAT hard drive. I don't know if this is the case, but I thought I would suggest something.

Also, just to state the obvious. Your example has two files that you are downloading that are combined to be around 40GB. So, you would need at least 40GB on your hard drive to download them. I think that the torrent client probably sets aside a contiguous space of 40GB on the hard drive at the start of its download (or it does something similar to this at smaller increments). That way it can simply fill in each of the packets as it gets them to build the files. So, you would probably need the full 40GB before it lets you start downloading the files otherwise it would crash or exit gracefully or something such. So, make sure you have enough space on your hard drive (and as I said above, make sure your hard drive is formatted as NTFS instead of FAT). That's all I can think of...hope it helps. Probably not, but maybe.