Hi Scott,
Is your Chrome 32 bit or 64 bit? If you have 32 bit Chrome installed, please do the following:
1) Close the Google Web Designer
2) Uninstall the 32 bit Chrome
3) Install the 64 bit Chrome.
4) Clear the Google Web Designer application cache. Cache location is C:\Users\<your username>\AppData\Local\Google\Google Web Designer\data\cache
5) Relaunch the Google Web Designer
Another reason which we can think of is that your computer is behind the proxy.
Hope it helps,
Rika
(Google Web Designer team)