ERROR: Too many forms are currently open, close some forms and try again

I’m having an issue with Axapta 2009.

I only have two forms open and I keep on receiving the below error message. Its random.

ERROR: Too many forms are currently open, close some forms and try again

This doesn’t make sense as I previously had more than 5 forms open at a time and I never receive a message like this.

When I click on the ‘OK’ button, Axapta just closes and I loose everything

Does anyone know how to fix this issue.