Hi Khaled,
The tech gurus will help soon, especially if they think I'm sending you in the wrong direction. So in order to help you sooner I give you this bad advice.
I would get a long patch cord, 100' or as needed, and make sure you have an excellent wireless signal by putting your wireless router in the midst of your exam rooms.
If that doesn't help I would borrow someone else's laptop to see if it's your machine, probably not if happening on more than one machine.
Finally for my limited brain, I would buy (buying is the only fun part of problem solving for me since I'm not good at it) an ethernet card for your machine and go from exam room to exam room dragging that very long patch cord, because I never get this problem on a wired network.
Hopefully the gods will see my folly and rescue you now, even if it is Thanksgiving Eve.
