Don't you just love these unambiguous questions... lol.
Especially when posters never come back to explain things properly!
Anyway, he did say "when text comes up on the screen", so it could have been over a 3D screen and the Sync was wiping his text out. But as he hasn't been back, I guess we'll never know!
As for the flashing bit, if I run just the following:
CLS 0
Print "Hello World"
End
It does not flash at all. (I'm using XP too).
However, I have seen the problem many times, but using CLS 0: Sync on the first line of your program usually stops it.
I'm fairly certain that it's only a Sync related problem.
TDK_Man