I am actually have the same problem on a new Mac Pro. Running Final Cut Pro 6.0.6 With a Raid Fiber Channel Drive. The Files are Uncompressed 8 Bit.
The Job was started on an older mac with slower CPU and less Ram running off the same Fiber Channel Drive and never had a problem.
I thought It could be the FCP setting but i have copied the same preferences over and still no fix.
MacPro4,1
Duel Quad-Core Intel Xeon 2.26 GHz
Memory: 8 GB