What kind of GPS reciever do you have? I would try playing around with this little program called GPSInfo. It should be able to scan what port your GPS is on. If you read the literature that came with the GPS it should say what baud rate to use. I have a Holux 240 bluetooth GPS paired to my 1945 with good results. It has worked very well with every GPS program I have tested. I even get decent signal indoors!
Check out GPSInfo, its free
http://www.easydevices.co.uk/downloads/GPSinfo.zip