GTM temporarily downgraded the version of the desktop app associated with the account for our organization, and it appears to have done the trick for all people who were experiencing the problem. Hopefully others can get a similar reconciliation.
Thanks for the help!
I will send you a PM right away. I've been experiencing this problem since today (Monday morning) on both GoToMeeting and GoToWebinar. I tried reinstalling, scanning for malware, the network wizard, and pretty much everything suggested in this thread! Even tried with my anti-virus turned off. Nothing! I can neither join nor star meetings or webinars.....and it all worked fine just a couple days ago. I would like to please get the software downgrade ASAP!