Donno Huehnerschaender, maybe its something todo with TImage or TCavas and the fact that I didn't sync..
Anyway it was only to show the genral idea, I stated in the code its not the "proper way".
If many insist on working with Timage (which I doubt) I can debug the app.. :?

What's your computer spec? maybe its something to do with the CPU or its utilization(?)
I tested it on K7-1200, 1GB ram, with a crappy PCI video card. i'll try it at home as well.