Issue booting new kernel

[Troy Knabe]

I updated all of my servers over the weekend, and one of them would not reboot.  The only way I could get it to boot sucessfully was to revert back to the previous kernel version.  I am unsure what log information would be helpful in troubleshooting this, so if someone is willing to help me troubleshoot it, I will provide whatever they are looking for. 
 
The original kernel was 2.6.9-42.0.10.EL, and the new one that wouldn't boot is 2.6.9-55.EL.
 
The hardware is a Sun X2100  with an AMD Opteron 148.
 
All of my other servers are running opteron based processors, and I have never had an issue upgrading the kernel release on any of them.
 
Thanks
-Troy