I also experienced the same problem that BigRon has described, once upgrading to FCP6. I never got this error in the past under the 5.xx version. I playback umcompressed at 20,3MB/sec with no issues. Now it won’t play back unless I turn off the Canvas window. Under FCP 6, it only plays from the timeline to my NTSC monitor. Prior to the upgrade to 6, it played just fine in the Canvas window and the NTSC.
I also received the same error message, BigRon listed in his original post. Is there anyone out there with an answer why now under FCP 6 it no longer works. Before I ditch FCP6 and go back to 5.1.4
I also use a G5 Dual Processor with 8GB RAM and 3TB of disk space
Dave