I solved the problem, and I hope my solution can work for you as well.
First of all, I realized that the problem was not on Navigator itself, but on the gps program of TomTom.
So I uninstalled it; at this point TT Navigator was back to normal, working as usual, but, of course, with no GPS support. Then I tried to reinstall it (latest release 3.03) and, surprise! It did not work again...
So (after some useless tries, like installing directly from the .CAB file) I simply run TomTom Wizard. I always said yes until I was asked if it was the first time using TT. I Answered yes, set up measure system and then said no to both proposed TT gps devices. After that the GPS dialouge window came up (NOTE: I usually could not open it, since it got frozen).
Then I simply selected my GPS model and (most of all!) port (which was set to com3, instead that generic compact flash). From that moment on TT3 was back to normal, fully working, at normal speed.
At the end, I don't think that reinstalling the program helped, just try the wizard.
Now I don't dare recreate the problem, but should it happen again, I will try this procedure again.
So, that's it. It worked for me (and I'm happy I will not have to start from scratch!), and I hope it will work for you as well. Good Luck!
