Tim,
This problem is due to JTWC changing their web site.
Here's a workaround until I can get a fix.
1. Start GT
2. Go to the "Manual Data Download Browser" (located at the bottom of the screen)
3. If you see the NHC page, scroll down towards the bottom to see a web link to JTWC.
3.a.  If you do not see the NHC page, type in www.nhc.noaa.gov in the address bar and click the go button.
4. When you are on the JTWC page and there are active storms, click on the JMV 3.0 Data link.  This should display the forecast advisory from JTWC.
5. You should also see an "Import" button appear.  Click on the import button.
6. You should be ready to plot the forecast for the storm.

Let me know if you have any more questions.
Bryan