Weird MDI problem, need some advice

The program that I have now has the following:
- main menu (mdi form)
- form 1 (mdi child of main menu)
- form 2 (mdi child of main menu)

Sequence of events is Main Menu -> Form 1 -> Form 2

Textboxes move from one to another through both the enter (requested by the user) or the tab key.

You call form 2 by clicking a button in form 1 and it shows up as an mdi child of main menu. The problem is when I close entry form 2, the enter key event no longer works for entry form 1 (form 2 will set focus to a textbox upon dispose) for the textbox, BUT the tab key works. Instead, the enter key actually opens up form 2 again! None of the key events (keypress, keydown, keyup) detect the enter key anymore. This problem does not occur when I do not have form 2 as an mdi child. I hope this isn't too confusing. Thoughts on this?