Hey guys, hope someone can help me.

You all know that the best way to model an existing object is to use blueprints (like for the ferrari tutorial). Well, just after importing the blueprints in all the viewports (View-> Image plane-> Import image) my troubles seem to start.
The perspective view works perfectly but the front, top and sideview are very slow. After making a cube, selecting the cube in the front view takes 3 seconds while in te perspective view that cube is selected instantly after clicking it. This is very annoying and I really can't work this way. Does someone have an idea what the problem might be?
It must be something with the imageplanes, cause when I delete them, everything works just fine.

Thanks in advance :-)