maybe somebody else can spot something, there is nothing about your specs that leads me to believe you shouldn't have less problems than me, not more.
i don't know exactly what a bridge is i must admit, i just know that last week i had to get a firmware update for one for the new 40gb hd i bought. while doing this and identifying my devices, the tech support guy (who was a supervisor, 1st guy tried to blow me and my problem off since he didn't know the answer) told me that the que bridge was the same as the one in my hd we were working on, so if it was working, we should be able to get the drive working too by updating. and we did!! but it is a little bit complex and you need tech support to talk you thru it. or at least i did. i still have all the stuff to do it with and would email it to you if i thought we wouldn't be taking a chance on screwing things up more. i will be talking to this tech rep next week about a different issue that he said he would help with. i will ask about this if you can't get qps to help. obviously this stuff is not just sitting out there on their website.
i can only think of 2 other things to suggest. slow your burn speed, maybe all the way down to 1x if nececsary, but i would think 4x would help. while your recording drive might work best at it's max speed, the read drive might not be able to keep up. and try waiting to insert each disc only when toast needs it. ie.- launch toast, click copy, insert read disk, hit record, insert record disc when prompted. roxio advocated this method with the osx beta and it might still be good advice with the final release.
i have also heard people suggest you only use discs that are max rated at the max speed of your recorder but i have never found this to be a problem. however if you are trying to record on 4x max media at 8x, it probably won't work very well. toast should keep you from doing this though by only allowing you to choose 4x in that case.