You can read more about GTA on Wikipedia in their article which is available here: http://en.wikipedia.org/wiki/Garner_Ted_Armstrong
You can read more about the events leading up to his demise from the CGI and his subsequent creation of both the GTA Evangelistic Association and Intercontinental Church of God by reading the paragraph "Post 1978 Ministry"...
Oddly enough, the people succeeding GTA didn't want to make any mention of the CGI in their announcement of GTA's death in 2003, since the webpage http://www.garnertedarmstrong.org/thisweek2.shtml reads:
Armstrong was founder of the Intercontinental Church of God and Garner Ted Armstrong Evangelistic Association, and son of Worldwide Church of God founder Herbert W. Armstrong, who died in 1986.
You will see in one of their online booklets "The Long Tradition of Prophetic Insight and Accuracy" [visible here: http://www.garnertedarmstrong.org/pubs/PropheticInsightandAccuracy.htm] that they are still playing the HWA-card. No mention is made of the many disagreements between father and son which are so well-documented by John Trechak in the Ambassador Reports, and an attempt is made to get tithes from people who believe they are still following in the footsteps of their great idol, GTA - a revamped edition of his father, HWA.
This organization is stuck in a time capsule with a decreasing number of donors as they die out.