Hmm ... that is odd. I have several of these with the Intel NIC's ... I'll keep my eye on them for any issues, but I've seen none thus far. Good luck.
The mouse and keyboard would pause every few seconds, for about a second. I looked at the CPU and it would be a jagged line up and down from 0% to 30% on only one of the CPU's. The machine is dual CPU, and it would show up as the 1st or 9th of the 16 showing (quad core with hyper-threading so you see 16). Checking processes would yield nothing, even the CPU time of processes did not show it after keeping it on like this over the weekend. If you started pushing processes on the machine to get it busy, all the CPU's would start doing the jagged up and down. They would follow each other exactly. It was some sort of interrupt issue since it would stop you typing and NOT queue up what you had typed. I have never seen this behavior before and I have been a Systems Admin here for almost 10 years.
It is fixed due to me pulling out the Intel NIC though, but I am pretty sure it is not the Intel NIC that was the issue, it is the crappy NetExtreme II onboard card.