Normal CPU?

I have a new 520 (V5R3) -- online less than a week -- that is running the 
exact same load as the 810 (V5R2) that it replaced.  Same configuration, 
just saved and restored from server to server.  Something is bringing the 
new server completely to its knees (97%+ CPU utilization) and I'm not 
seeing what it is, so I'm wondering if anyone can provide ideas where I 
should be looking.  Originally, it appeared to be an SMTP issue and 
bouncing the SMTP task temporarily would resolve it, but I tried that a 
short time ago and never saw the CPU dip below 60% (the vast majority of 
it being the Server task).  We are a small shop and a third of my users 
aren't even on the server, so I can't imagine that we have legitimate 
traffic hitting me this hard when the old box would handle everything we 
threw at it without a problem.

Thanks in advance,
Patrick