Computer suddenly stopped recognizing MEGA 2560.

I had been modifying a circuit and program on my Arduino MEGA 2560 for several hours before testing it in lab today and everything worked fine until we started in the lab. The problem I am experiencing is that when any Arduino is connected to my laptop, it is only available to upload a program on rare occasions. The Arduino turns on and the L and On lights come on, but the TX does not flash like it does when it is attached to other computers. Essentially, there is a serial communication problem between only my laptop and various Arduinos, so my laptop must be the source of the problem.

I have tried reinstalling Arduino and checking to see if the Arduino is recognized as such in the devices list, which it is. Does anyone know what I did to cause this or how I can fix the problem?

Houdyschell_Lab:
The problem I am experiencing is that when any Arduino is connected to my laptop, it is only available to upload a program on rare occasions.

What exactly do you mean by that? Is it not showing up in the Arduino IDE's Tools > Port menu?

Houdyschell_Lab:
checking to see if the Arduino is recognized as such in the devices list, which it is.

Even while you're having the "not available" problem?

Did you try to look at the device manager if it sees an unknown device?

is there a sound created by the laptop or pc when you connect the arduino to it?