Screen flickering on X220t

[lotsawa]

Since some months the screen of my X220t shows some fine, grainy flickering from time to time. I think it only happens when the second monitor is attached and I think is depends on how heavy the CPU is loaded with work. First I though it might be a Linux driver problem (Ubuntu 14.04), but then it also appeared within Windows 8.1. Sometimes it helps to disable the LCD for a while in the system settings or even just switch into terminal mode and then back into graphics mode, but sometimes I have to reboot.

I don't know what this means, I suppose it's some kind of a hardware problem. Maybe it has to do with high CPU / mainboard temperature. Today, when the flickering occured during a video export and the CPU had to work hard, psensor showed 96° Celsius.

Any idea?