There is a solution! Use an application from GoToMeeting called “g2mtranscoder” which allows you to convert the file from GTM format to standard WMV.
Here’s how I did it in Windows 7:
Navigate to your GoToMeeting program files folder. Typically this will be in C:\Program Files\Citrix\GoToMeeting\320.
Copy your GoToMeeting recording to this directory.
Open the command line. On Vista / Windows 7, click the Start button and in the search box type: cmd and press Enter; in Windows XP, click the Start button, select Run, and type: cmd and press Enter.
Type: cd C:\Program Files\Citrix\GoToMeeting\320\ and press Enter. This should take you to the GTM directory.
Type: g2mtranscoder source=GoToMeetingRecording.wmv (replace with the name of your GTM video).
Hint: you can copy and paste into the command line window by clicking the C:\ icon from the command line window and selecting Edit > Paste.
Once the conversion has completed, simply open the file in Camtasia using File > Import Media, or use your favorite video editing software.