xircom rbem56g-100 modem in windows 2000 problem

[SPICERTWO]

I have updated a Dell Latitude CPt to windows 2000. When using the xircom rbem56g-100 pcmcia card, in the device manager all the drivers are installed and the network works. Only the modem is not responding. After searching, I found that some irq or memory error should be the reason for the blocking problem. The latest drivers doesn't work, we can't update the modem? Also in another pc or OS, it gives the same error. We don't think the modem is broke but before it worked under windows NT. Inserting another type of Xircom gives the same problem. Anybody knows a solution