I have facethis error a lot of times. This usually happen when you add/delete a column from a custom module class and don't regenerate the code.
You can go to
Modules -> "YOUR CUSTOM MODULE" -> "YOUR CM Class" -> Code -> Click "Generate Code" button.
Generate and save the code and then try to take the export of the package.
This should solve the problem 99% of the times. Are you getting some missing column error in the error message?