There's are strange grey lines appearing on a computer when it is connected to a terminal server. The display on the right is from an external monitor, the one on the left ist from the Laptop. When the external display gets turned off, the lines appear on the Laptop's display. However, when the user starts Word directly on the Laptop, there are no lines.

When connections are initiated from other computers or other users, there is no display issue either. Also the lines cannot be seen from another computer via isl light client (remote-support tool).

Horizontal grey lines on display-allpack_bildfehler.png

What irritates me most is the fact that the lines are not completely from left to right but are all intterupted on the white background regardless of the window border or the page layout from the shown Word document. Also that the picture is a screenshot and didn't need to be done with a camera to see the lines is strange after they didn't show up during remote support.

Any suggestions concerning the most probable cause - graphics card failure, driver issue or something else?