ofFbo allocation stops after several seconds on macbook Air

I have a bit of code in which I allocate a new ofFBO based on whether I am using a movie or an image for this project.

I don’t want to use a pre-allocated (in Setup) off because the dimensions will change based on what is being used (movie or image)

What is happening right now is that, after a few seconds of the program running the off is not being used, and I get an error message:
[ error ] ofFbo: FRAMEBUFFER_UNSUPPORTED

ofFbo saveThis;

if (!playMovie){
      saveThis.allocate(backDrop.width,backDrop.height, GL_RGBA);
} else {
       saveThis.allocate(theMovie.width,theMovie.height, GL_RGBA);
}
    
saveThis.begin();
   ofClear(0,0,0,255);
saveThis.end();

I suspect it is a problem with the paltry memory on the Air’s graphic card. I am not using the movie allocation at this time, so it is just the image one which is causing problems at this point.

This code is basically preparing an FBO for drawing into to enable saving to a file at a higher resolution than a screen grab would do.

Any help would be appreciated. This code works flawlessly on a mac Mini.