You have to remember it's just a Beta, and also if you use private trackers, some may not allow Limewire as a download client. I've had trouble with one or two myself (Can't remember from which site, cause I tried a few. Think Dime was one of them)

On the torrents that say need more sources you could try an alternative app. like Azureus.

I'm sure that improvements will be made to Limewire before the final release.