i've had this problem too on my nf4 based barebone, but after i'm using wlan now and deleted the forcedeth.kext i havent the problem anymore.

using zeph 10.5.2v2 on shuttle sn26p (nforce 4 SLI, opteron 165(using both cores), 2 gb ram, gf 8800GTS 320 and sata HDDs