Serial port problem

[Alan Garrison]

In my server (Debian slink) which runs my dialup, I switched 
out the old motherboard and up in a new one (new Super7 board).
Just the motherboard, and cpu were changed, all the other 
hardware is the same.  Everything works except I can't do 
anything with my modem.  My PPP script just dies, and minicom 
loads but it doesn't get any signals back from the modem.  
I tried using both /dev/ttyS0 (com1) and /dev/ttyS1 (com2).  
The boot message says something like:

/dev/ttyS0 (IRQ4: 3f8) 16550A
/dev/ttyS1 (IRQ3: 2f8) 16550A

(note: I'm typing this from memory, what it actually says is 
probably a little different).  It seems that the kernel 
sees the ports as 16550A UARTs.  I am running kernel 2.0.36. 
Any ideas?  (If it's not already obvious, the modem is 
external and worked perfectly fine on the older board).