Problems with some laptops on a 5100MP Projector

We have 5 5100MP projectors and on 2 of the 5 we have strange problems, on the 2 units, if you connect a laptop for example a latitude E4500 and use the F and screen change screen I think its F6 the screens will cycle on the laptop and projector but the projector will not do a mirror of the laptop screen. When i say mirror I mean both have the display, laptop and projector. I can have it on one or the other but not both, the projector will do extended desktop but not mirror. When I put the same laptop on 3 of the 5 projectors it works fine. The laptop has the newest Bios and video drivers installed. Anyone have an idea of what is going on? 

***Note, that some laptops work fine on the 2 units that wont work with the E4500 and a few other dell laptops.