After Effects on the Mac often renders slow for me. Anyone using AE on the Mac have this problem?

Seems to be an issue with writing files to the hard drive. The same thing that takes about two minutes to RAM preview, takes about 20 minutes to render. I look at the CPU usage, it is low, like 20% or something, but my whole machine is crippled until the render completes. I cant even try to check my mail or the web without getting a spinning beach ball.

Any ideas?

Thanks!

PS: I'm working with a Mac Pro, details below. My working hard drive is a Barracuda 7200.12 SATA 3Gb/s 500GB.

Model Name: Mac Pro
Model Identifier: MacPro4,1
Processor Name: Quad-Core Intel Xeon
Processor Speed: 2.66 GHz
Number Of Processors: 1
Total Number Of Cores: 4
L2 Cache (per core): 256 KB
L3 Cache: 8 MB
Memory: 8 GB
Processor Interconnect Speed: 4.8 GT/s