Monitors aren't shown.
 

I have two Dell Inspiron 7000 series laptops. I also have three Dell 3100 docking stations. With laptop (A) on docking station (1) all four monitors show up (The laptop and three external monitors). With laptop (B) on docking station (1) only three monitors show up with the option for the fourth monitor to be a duplicate of the laptop's monitor. With both laptops (A) and (B) on docking station (2) and (3) only two monitors show up. Any thoughts?