If you downloaded the GBDeflicker 1 Plugin for CS4 recently, you may have been unable to activate the free trial.
If that happened to you, please download the newest release (version 1.5.14). After you install this new release, you should be able to run GBDRegister and activate the free trial. The older version (1.5.13) had a trial license that expired on January 29th, 2012. Dang! I hate it when that happens.
I'm sorry if this caused you any inconvenience