TVout flickering

I'm using this library to output date to TV: Google Code Archive - Long-term storage for Google Code Project Hosting.
In demos, it works nice, but when i try to display my own data, i run into some problems. (I'm using Duemilanove on PAL TV)

My init string goes like this:

void initTV()
{
TV.begin(PAL, 128, 96);
}

Then, in loop() i call

TV.delay_frame(1);
TV.clear_screen();
TV.print("few lines of text....");

It works nice, but.....
If i write 2-3 lines of txt to the screen it looks ok, but after 4th or 5th line txt starts to flicker (previous lines are still ok)

Any ideas how to make it work properly?