Go to the azureus support forums, they have some workarounds for Intel macs. I had the same problems, and couldn't get it to work even with the workarounds, though. I used Bits on Wheels, but it runs slow as molasses on the Intel Macs for some reason. I know, because the same torrents are blazing on Azureus on my PPC. So... you know. Check out the azureus site again, they may have made progress since last I checked.
Edit: The build of azureus they have out now is not Universal, so you have to copy things from your Library into the program to replace the azureus versions. Read the forum, it'll explain better.