To Fax, or Not to Fax....

[#1]

Spcification: FTTC broadband, Windos 7 Pro. Zoom USB modem.  Ever since I have my connection to the internet upgraded I have not been able to send/receive fax messages.  I'm an accountant and it is useful to be able to quickly communicate with the Inland Revenue.  Having just re-installed the software and then plugged the modem in I get the "The fax could not be sent because of an unexpected error" message.  I have tried every test I can find, including querying the modem in Control Panel/Devices (shows that it is working!) so I am leaning to the belief that it could be something to do with my line as it is?  Any assistance will be appreciated please.

[#2]

Sounds more like the software to me.  What happens when initiate a call?  Does the modem grab the line and get as far as dialling?
Is it Windows Fax that brigs up the error?
http://answers.microsoft.com/en-us/windows/forum/windows_7-windows_programs/windows-fax-cant-be-sent...
http://social.technet.microsoft.com/Forums/windows/en-US/07b8c81a-80fd-4a86-9669-a9aaffe707fc/the-fa...

[#3]

Yes, it is Windows Fax that brings up the error. 
Now after reading both of the conversations in your links [thank you] I have a better idea of what to do.
Scurfing the web I downloaded the manufacturer's latest driver for my modem [and their set-up instructions - which are different from those on the original Cd] and re-installed it per the latest instructions.
I am happy to report that the fax is now working. 
I suspect that windows updates somehow interfere with the driver.
Anyway, once again Thank You" for your positive assistance, it was much appreciated.