I upgraded to OS 10.6 and there a no longer any problems with the hard drive test.
The Novabench test for hard drive speed hangs when running either the full test or just the hard drive test. All of the other tests complete fine. Any ideas? OS 10.5.8., iMac5,1 (20"), Core 2 Duo @ 2.16Ghz, 2GB RAM at 667MHz, ATI Radeon 1600, 250GB HDD