PCMCIA Modem causes hang on boot

FreeBSD 5.2-CURRENT #0: Tue Jun  1 00:00:38 CDT 2004
gcc version 3.3.3 [FreeBSD] 20031106

PCMCIA Modem: Hawking PN612: 56Kbps V.90 Data/Fax PCMCIA FAX/Modem


Hello:

 FreeBSD CURRENT hangs on boot when I use this PCMCIA MODEM. The laptop will not respond to CTRL C. I have to do a hard reboot. I get the following messages just before the hang:

sio4 <Intelligent PCMCIA FAX + MODEM> at port 0x2f8-0x2ff irq 11
      function 0 config 23 on pccard 0
sio4: Type 8250 or not responding
sio4: Unable to activate interrupt in fast mode - using normal mode.

 After this last message the laptop hangs and I must press the power off button. Any advice
on what may be wrong would be appreciated. The manufacturer claims that it uses a Hayes AT compatible command set. Theis PCMCIA modem also works under Linux.

                         Kind regards,
                         Jonathan