hmmm... no problem for me. in beta4 also overclocking for the first time on zaurus doesnt affect the display (no distortions or interferences).
Maybe a solution would be to change the COM ADJ settings in the D+M Menu.
After installing the new bootloader for beta4 it seems that the settings for my LCD got lost (i saw this "ghost windows" again... in D+M menu I saw that this settings were at default again).