Go to the game's install directory and open the NCSA-Live folder (default is C:\Program Files (x86)\GRO\NCSA-Live)
Either change DisplayRefresh=60 to what your monitor supports at the current game resolution, or,
Edit any of those to set the resolution/refresh rate/windowed mode to your liking.
ex. for 1280x720 @ 60Hz in Windowed mode:
Should fix your problem.
No need to contact support, just file a bug report with the beta as it's being caused by poor auto-detection of your computer's settings. Fairly uncommon in release versions, but still happens nonetheless.