validation, onClick events, and the page lifecycle

i am having a problem with the custom validator control not working properly which i think stems from a fundamental mis-undertanding of the page lifecycle, even though I have read http://msdn.microsoft.com/en-us/library/ms178472.aspx, it doesn't really answer my question.

I have a complex page that has a lot of code firing on page_init and page_load - which may be part of the problem......

The issue is that my custom validator evaluates the isValid object properly, however I cannot seem to figure out how to stop the page from processing anyway. 
When I click the "submit" button, by definition, a custom validator is supposed to run a check that is coded in the cvTest_ServerValidate event, and thus prevent the page from posting back if the validation returns false, is it not?
Anyway, when I run the debugger, I notice t ...