Denise;
Did you use the correct adapter? I use a KeySpan High Speed USB-Serial Adapter (USA-19W), Keyspan makes several different kinds of Serial/USB adapters and *this* is the only one that will work with the Pronto.
It might be the same for Belkin. When I was researching which adapter to use, I came across this about Belkin;
"I used the Belkin USB - Serial adapter, and it worked great. The model number is F5U103.
[Link: shop2.outpost.com] "
MIKE