SMP kernel and modem support

Newbie question. 

I'm running kernel 2.6.8-2-smp on a dual Pentium 3 system, using debian 
sarge. 

My modem runs without additional drivers under a uni-processor 2.6.8 kernel 
but the system cannot find the modem when I use the smp kernel. 

It's a hardware modem, not a winmodem or linmodem. 

What should I look at to get the modem working with the SMP kernel. Is this 
a matter of installing extra software, do I need to recompile the kernel..? 

A pointer in the right direction would be useful. 

Regards 

 - Joe