Flashing on some displayed data with WinXP

When I click on the upper right to go to full screen on my WinXP system some data starts to flash with updated. If I go back to non full screen the flashing stops…

The following data lines flash all the time in full screen display mode:
Temp Rate
Windrun (including label)

The following data lines flash sometimes in full screen display mode:
Temperature
Wind chill
Due point
Wet bulb

WinXP-512megs memory, Version 9.91, Ultimeter 2000

i just tried in windows 20000
it does not do that
must be a xp thing