[CentOS] Strange slowdown occasionally in CentOS 5.0

For some reason, parts of my system are now slowing down to an
agonizing crawl from time to time.  At first it was my VMWare Server
1.04, which became such a pain that I rebooted.  Then, it looked like
it was a network-induced thing because the prime culprit was
SeaMonkey, particularly with multiple tabs open.  I did an ifdown and
ifup on my NIC and that seemed to help for a while.  But then it hit
OO and I'm baffled.  It seems that the second time I open any
document, particularly with OO Writer, the load and save times are
dramatically extended - we're talking five to ten minutes.

I don't even know what information I should include here that might
help, but here's what I have running at the moment:

OS/Hardware Config:
OS : CentOS 5.0 (2.6.16-8.1.6 Linux kernel) x86_64 with latest updates
CPU: AMD Athlon 64 x2 4200+
M/B: ECS NFORCE4M-A
ram: 2GB OCZ DDR2 800 (PC6400)
hds: 160MB + 120MB Maxtor PATA UDMA-133 (160 is the boot drive)
sds: 300GB Seagate SATA-150/300 (/boot and / are here)
        320Gb WD SATA-150/300
vid: geFORCE7100gs (nVidia) PCI-E x16
lpr: Minolta QMS PagePro 1100 laser printer on /dev/lp0
mod: Agere Systems 56k WinModem (Lucent)
nic: onboard (mobo-nvidia)

Any suggestions or more information needed?

Thanks.

mhr