I was working on a Microsoft Access 2003 application that had Visual Basic code sitting behind the forms that it had. I was able to set break points in the application and the debugger would break when it hit them.
At first I thought it might be a bug in the code and so I dropped some MsgBoxes into the code - and they were getting displayed - so that wasn't it.
Googling - the answers to this problem were just not good: export all your code, delete the modules and re add them - I had way to many modules, that this just didn't sound like a path I would like to take. After searching high and low, I figured out the problem had to do with a single check box on the startup page!.
The "Use Access Special Keys" needs to be checked on. (If it isn't for you, set it to checked, hit OK and then close and reopen your Access file - as the setting takes affect only when the database is being started up)