After quitting X today I noticed that the disturbed picture I usually seen on my tv then had the some colors which were on my vga (text) console on my computer monitor. And indeed, clearing the console cleared the disturbances on tv also. The same thing happens when switching to the CRT vga (text) console while X ist running.
So the problem seems to be that the driver tries to give a console on the tv, too. With Option "ConnectedMonitor" "CRT" the vga (text) console on my computer monitor is fine again when switching while X is running - no bug #3 (see earlier posting), but I do not have a second screen (tv output) under X.
Maybe the problem will disappear if the driver stops TV-out when witching to a vga (text) console with a CRT attached.
So far, there seems to be no option available for this, is it?