Core Locks up every 15 Mins - DHCP appears to be the problem

I've installed LMCE 0710 RC2 - Got through the installed and configured 1 MD. Core is the only DHCP server in the home. After about 24 hours running good, the core began to lock up about ever 4 hours or so. Now it's locking up ever 15 mins. Review my configuration for everything and only made a few changes from default install as follows:

MD - Set Video to Manual as it was a sugesstion in another post to get Dolby/DTX sound out of system - that worked.

No other mods.

Upon investigating, I turned off DHCP on the core and the system has been up for an hour with no lockups.

I'm not sure how to troubleshoot DHCP in Linux as I don't completely know my way around, does anyone have any sugesstions on how to investigate the DHCP "possible" issue ?

thanks