USB modem disconnections

Hello all,
I have a problem with my ELSA USB 56K FUN modem. I’m running windows 2000 server, and I use it to share out my connection to other pc’s.
When it works it works great but recently I rebuilt the pc and an odd problem has occurred. Every now and then though my modem disconnects from the ISP and I can’t reconnect, but in the system tray it shows the small network icon flashing as normal as though everything is fine and dandy. I know the modem has disconnected because I hear it disconnect and I can’t browse any longer. The result is the modem/internet icon never disappears and I’m never able to reconnect. The only way to get around this is to reboot the system.
Thus far I have reinstalled the Win2000 drivers for the modem however the problem has started to reoccur. I’ve also disconnected all other usb devices but again it occurred.
So does anyone know how I can stop this happening or is there any process I can kill off which will stop me having to reboot.
As ever I’d appreciate any advise.

Cheers



Greg