The S&T works fine. You didn't post which version you have, 2006 or 2007 or the gps skin file. Probably you're losing the focus when you call S&T. Set it up as the external GPS in the exectbl.ini file.
For GPS indicators to work make sure you have a com splitter for the GPS receiver working. They have to be on a different com-port than your GPS program. Make sure to have indicators for your skin in you're using the North, south, etc directions..