Wierd Network problem

[Craig Russell]

I have a dell poweredge 6650 installed with freebsd
6.1 and on the local router, everything works great
(ie, a computer on a different subnet off the same
router can access it fine) but coming from outside of
the network access is incredibly slow.  My first
thought was that it must be a routing issue, but I
have two other freebsd 6.1 servers on that same subnet
and I can access them fine from outside.  I dug a
little further and compared the servers that are
working with those that are not and these are the
differences that I have found.

On the servers that are working (dell poweredge
2450's) the interface is an fxp0 and here is the
output of ifconfig:
fxp0:
flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu
1500
options=8<VLAN_MTU>
inet6 fe80::2b0:d0ff:fee1:f66a%fxp0 prefixlen 64
scopeid 0x1
inet 64.25.218.2 netmask 0xffffff80 broadcast
64.25.218.127
ether 00:b0:d0:e1:f6:6a
media: Ethernet autoselect (100baseTX <full-duplex>)
        status: active

on the server that is not working:

bge0:
flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu
1500
options=1b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING>
inet6 fe80::211:43ff:fedc:9aa2%bge0 prefixlen 64
scopeid 0x1
inet 64.25.218.10 netmask 0xffffff80 broadcast
64.25.218.127
ether 00:11:43:dc:9a:a2
media: Ethernet autoselect (100baseTX <full-duplex>)
status: active

The first thing that i noticed is that on the option
line there is quite a bit of difference between the
two.  So using the command line ifconfig tool I
removed RXCSUM, TXCSUM from the bge0 interface. 
Voila!  Speed increased and the server was actually
accessible from off net.  Unfortunately, as soon as I
tried to access any other port, the interface crashes.
 Eventually the watchdog picks up on that and restarts
the interface.  But the problem is completely
repeatable.

The server that I am having problems with is running
cpanel 10.9; the two that are working are running the
dns-only version of cpanel.  I am not picking up any
errors in the logs.  This could be related to cpanel,
or not, I'm not really sure, although it shouldn't be.

The other unique thing about the setup, that very well
may be affecting is that the router in question has
two subnets configured on the internal port.  There is
a nat'd subnet for our local users and there is the
public subnet that these servers sit on.  The final
resting place for all three is in a datacenter that
isn't built yet, so rather than reconfigure everything
once that was done I simply routed the final subnet to
our office and set it up their.  The router is a
mikrotik RB112 board which only has one ethernet port
so I couldn't dedicate a port for the new subnet.  As
I said, my first thought was that the problem was in
the router, but the other two servers are running
fine.

Any suggestions?

Thank you, 
Craig Russell