Grid View has a method that is unfortunately protected called Extract Row Values.
I know its very annoying and hard to get the data out of the data controls (gridview in this case), but there are other things you can do to make it easier.
Yes, I did put the breakpoint at the Row Updating line (and not in the function).
You have to make sure that you aren't setting your Grid View's data when it is not postback.
Do you have some sort of Java Script functionality that may be stopping it? A common problem people have with Grid Views is understanding when to data bind the data source to the Grid View.