Chances are you disabled Events in one of your code blocks, and didn't re-enable it.
In order to avoid changes made by code triggering itself and getting caught in an endless loop, this line of code is often used:
Code:
Application.EnableEvents = False
This disables the automatic running of your event code.
However, it need to be turned on again as your code finishes running, or else the "automatic" code won't work anymore.
So any block of code where you have the line above, you will also need this line at some point after it:
Code:
Application.EnableEvents = True
However, if you exit the code before getting to this last line (either because you placed it in the wrong place and are exiting before hitting it, or because your code stopped because it hit an error), you will experience what you currently describing.
You can just manually turn it back on by running this short little procedure.
Code:
Sub ReEnableEvents()
Application.EnableEvents = True
End Sub
And make sure that you address any parts of your code that could be causing this to happen.