read the 'debugging vba' link. Good one, but would add that sometimes you can end up with 'ghost' breaks - code that continues to stop at a line you removed a break from. This can happen even after you close and reopen the form (assuming one is involved). If you're like me and compile frequently during code changes, the option to compile isn't usually available if this problem arises. Thus I cannot say that simply compiling will solve the problem, but can say that if you make any small change to the code, save the module, undo the change, save and compile, it will get rid of the ghost break.
Also, stepping through code that uses any "active" property such as .ActiveScreen will not perform as expected because the expected object isn't active when the code editor is the active window.
Just my 2 cents.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.