Do the ones that aren't downloading say "queued" or "Active 0, Busy #"

Are you downloading things with a score of one or two? The lower the score the less likely you are to conenct and be able to download.

Are you trying to download MP3's with the first letter missing and file sizes in the hundreds of megs? You can't download corrupted results.

That's about all I can think of at the moment.