[CentOS] Problems after update to 5.5

Sat May 15 11:27:45 UTC 2010
Colin Coles <colin at wemoto.com>

Hi,
 I have updated 8 machines so far and 2 are refusing to boot on 
2.6.18-194.3.1.el5 kernel, they just hang at: 'Starting udev:' but when I 
revert to 2.6.18-164.15.1.el5 kernel they boot fine. Any pointers?

Cheers,
Colin.