Ethernet Card Weirdness

[T. Wood]

Hopefully my question will be more clear and precise than my subject line.

I am using RedHat 6.2 and pmfirewall to perform IP masquerading and
firewall services for my home network (currently 1 Win98 computer and the
RedHat server.)  I get my internet access (via static IP) from att at home
into eth1, a SMC 10/100 card using the rtl8139 module, and eth0 is a
Compaq 10bT card using the tlan module.  Win98 is using a Linksys 10/100
card.  (I think) everything was working fine, so, being a moron, I decided
to switch the ethernet cards so that I would have 100bT within the
internal network.  This is when things went awry.
	First I stopped pmfirewall, then I ifdown'ed eth0 & eth1 and
rmmod'ed tlan and rtl8139.  I switched eth0 and eth1 in pmfirewall.conf, I
switched eth0 and eth1 in conf.modules and I edited ifcfg-eth1 and
ifcfg-eth0 to switch the IP addresses and gateways.  I then switched the
ethernet cables and rebooted my modem.  Next I insmod'ed tlan and rtl8139,
ifup'ed eth1 and eth0 and started pmfirewall.  I think everything "worked"
at this point, however my connection from Win98 had dropped from a normal
average of 300kBps to a trickle, a crawl... 
	I switched everything back and all seemed to return to normal
(ifconfig shows a ~10% collision rate on eth1 (outernet) but that could
have been happening before and I just didn't notice)
	So does anyone see something I forgot or did wrong?  Why would
switching eth0 and eth1 cause such a slowdown?  The list of commands and
steps I went through comprises about 75% of my linux knowledge, so if you
have suggestions or questions, the more detailed the better.  (I think I
ruled out pmfirewall as the culprit, but...)

Thanks

-Toby


Specifically the ethernet cards were:
SMC1211TX EZCard 10/100
Compaq Netelligent 10 T PCI UTP, Rev. 16