That's why you should not distribute programs yourself (unless you wan to be a maintainer and you want to keep an eye for new versions and update your repository). There is repositories, where latest versions can be downloaded and novice users can use them from GUI.
There is a rule never give links to exact version of a package unless you really want to link to exact version. Instead link to latest version (a special link which would be automatically updated).
If you want to install these packages from console, you could tell people to use "apt-get install <packet>" which would take latest available version.

If you do not follow this rule this leads to user confusion, accidentaly they choose old versions and old "hackish" methods when new clear methods exist.
In ussd-widget settings (accessible by clicking on wrench icon in desktop layout mode) there is field for parameters, that should be passed to ussquery.py.
Can you please try
ussquery.py <USSD code>
for example for my operator it would be
ussquery.py *100#
ussquery.py *100# -t 300
If it still fails, can you please try starting pnatd and entering (you would not be able to alter entered symbols in pnatd)
and copy here what it produces.
I have looked through standards again. Call forwarding is call forwarding, USSD is USSD, this are different things. Call forwarding exists on other tipes of networkd, USSD is specific to USSD. The fact, that call forwarding requests can be entered through your phone keyboard with special codes:
http://en.wikipedia.org/wiki/Call_forwarding
does not mean, that these codes are USSD numbers. Phone processes them in a different way.
So USSD widget works only with USSD codes and doest it a much better way, that usual phones (we will see, what nokia would implement).
Call forwarding widget works with call forwarding, again in a better way, than phones. If you don't like how it works write to call forwarding widget author, may be he will fix it or tell you why it is impossible to do it.