Black Screen with remote Desktop Connection

Hi, I have a server with O/S Windows Server 2008 R2 SP1, Foundation ED only 2 laptops connect via Remote Desktop Rconnection, we only use it to access Quick Books and some ms word and ms excel files nothing fancy.

Sometimes when I minimize my terminal connection and then want to go back in I have a black screen it takes a few minutes and then I am back in, I didn’t loose the internet or anything since I am still on and the other laptop is still working fine with the terminal connection?

I had Dell look at it but there couldn’t find anything.

My Internet provider is Comcast and I use there modem

Any ideas what the cause could be?

thanks