Follow these steps to correct the modem disappear problem in Windows:


1) check the modem firmware version with ATI1I2I3 command, if the version is 1.32J and higher (UPCI), then goto step 6

2) download flash wizard here:
ftp://ftp.multitech.com/utilities/flashwizard/flashwiz1085.exe

3) download modem firmware 4.32e (old PCI) or 1.32J and higher (UPCI)

4) use Flash wizard and upgrade modem firwmare ONE at a time.   DO NOT select ALL the modems to be flash at the same time in flash wizard.

5) after all the modems are upgraded, use hyperterminal to check each modem and make sure the firwmare show the new version.

6) remove all the modems mapping in Windows control panel.

7) use hyperterminal and for each of the modem, issue command AT$P0 and AT&W

8) reboot Windows and make sure there are no modem mapped in control panel.

9) Add each individual modem manually again and DO NOT auto detect the modem,  select ISI5634PCI-8 PCI 56K modem.

10) After all the modems are added, reboot Windows to make sure all the modems are still active in the Phone and MOdem options under control panel.