We have this issue and have found that we're not the only ones; here is a
quick description from http://www.developerdotstar.com/community/node/334:

This appears to be a bug. I can't get the debugger to stop on a line of code
in a script task in an event handler. Strangely, if I set a break point in a
script task in an event handler, a VBA code window will pop up for the first
script task in the package (even though the breakpoint is not set in that
task), but there will never be a break in the task where I set my breakpoint.

Any idea anyone?

Hello Florence,


Which build are you using? Have you applied SP1? I am seeing some other
stuff with your situation in SP1 but wanted to know on which build you were
testing.

allan