momentary freeze ups

[Todd And Margo Chester]

Hi All,

I have two computers running Xfce 4.8.  One is running Scientific
Linux 6.2 (RHEL 6.2 clone) 64 bit and the other is running
Fedora Core 16, 64 bit.

Occasionally, in any program, the computers will freeze up from
anywhere between five seconds and 20 seconds.  Then recover as if
nothing happened.

"top" shows hardly any CPU activity.  "free -m" shows three times
the empty space as used.

Is there some kind of file indexing going on?  On the Gnome side,
I know they have something called "tracker", but I don't see it
in Xfce.

32 bit FC 16 Live CD does not "seem" to show the freeze ups, but
it is hard to get a good test as most of the native programs are
not usable.  Prior to wiping and installing 64 bit, both these
machines were running 32 bit (CentOS 4.x and CentOS 5.x) with
no freeze ups.

Any idea how to troubleshoot this?

Many thanks,
-T