Kernel 2.4.26 and 2.6.6 starnge

[Debianzac <fabio.zagami@poste.it>]

I use a Dell Latitude CPi A366, to Woody V.3 R2, Kernel 2.4.18, all run 
perfect.
Ihave tested the kernel 2.4.26 and 2.6.6, but the modem in PCMCIA  
Xircom CBEM56G-100 ethernet + Modem 56 K, no work, the ethernet  working 
normaly.
The kernel 2.4.26 detect the modem in ttyS4 but show the message
" LSR safety check engaged" and don't work. The kernel 2.6.6 not detect 
no one ttyS.
Same one can help me?
Thanks