Anybody come across this issue?

My laptop workstation setup was working fine but recently it has developed an infuriating problem with both mouse and trackpad freezing
for a second every 4 or 5 seconds when I have my Dell U2713H (2560X1440) plugged into the thunderbolt port.
As you might imagine, this makes working in this setup practically impossible.

I don't always have the second monitor connected so I cannot make a connection as to any event/installation etc that might have triggered the issue.

I have the latest Nvidia driver installed and I tried updating the Dell driver also but no resolution to the problem.

The laptop is a G750JX running windows 8.1 and all important updates are currently installed.

If anybody has come across something similar or can help me troubleshoot I would greatly appreciate it.

Thanks