H300 - strange pixel problem

[PatOne]

I have a strange problem after installing the new release 3.0 on my H320.
The installation works fine, Bootloader ok, Rockbox starts.
But when the OS has loaded and I use the Up/Down Button in any menu, some undefined "lines" (like a triangle?!) are moving up and down over the screen and deleting fragments of letters and making them cloudy so that you can not read the words any more.
The same in the play mode - it seems that a not truely visible equalizer is working in the front of the screen and blurs everything.
If the player went in standby mode and you switch it on, the screen is ok until you move the up/down button again.
 
The original firmware works fine without any problems.

I've installed rockbox twice, one time automatically and the other manually - no positive effect.
The same with changing the themes/fonts, nothing helped.
Has anyone the same problem ?
What can it be ?

Thx
Pat




// EDIT //

I've found a thread in another forum with the same problem. Conclusion is that rockbox has agrassive timings with handling the LCD. Some older players have problems with that timings why the Display makes some pixel errors.

To solve that problem you have to modify these entries in the iriver system file to
CPUFREQ_MAX - 15, CPUFREQ_NORMAL - 5, default - 0