Monitor is flickering when changes on the screen (i.e. cursor)

[Flo <debianflo@gmx.at>]

Dear all,

I installed jessie with LXDE, 3.16.0-4-amd64.

The problem I am facing is that when I move the cursor or when there are
other changes on the screen like moving lines the Monitor starts to flicker.

The monitor&computer isn't new, there was Debian installed a few years
ago and there it worked.

The difficulty for me is that I don't know where to start from to find a
solution.

Can anyone give me a hint?

Thany you very much in advance.

Regards,
Flo