2 general questions to see if I can help:
1. Does this happen EVERY time you try to test ANY of your own 2D levels? Because, if this is your first time making one, you might just want to start your map over.
2. If you change the level to 3D mode, does this problem stop, only to start again when you convert back to 2D? Because, if it does, then I have no idea how to help you.