I was struggling to find a way to debug event handler scripts in SSIS, and thought I was missing something obvious (as did Jamie). Thanks to Daniel Read (again) I now know that I'm not the only one:

b) Cannot debug script tasks in event handlers. 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