I noticed that the TeamViewer_Desktop.exe process on the remote PC is using a lot of CPU. It is 50% of a 4 core CPU (Intel Q6600), so it is higging 2 cores just for itself.
I tried to set "Optimize for speed" but that makes no difference.
First this happened with version 11, so I updated (both remote and local system) to TV version 12.0.72365. It did not help. The CPU usage is still at 50%.
The remote system is running Window 7 Pro 64 bit in safe mode.