tif files saved in vuescan can not be opened in Painter?

Painter IX.5
WinXP

Hi there,

occasionally when I scan in negatives (you know, that thing 
photographers used until not very long ago... chemicals and all... :D ) 
I save them from Vuescan in an uncompressed TIFF file.

When I try to open these files directly in Painter, the app complains 
that the tif file seems to be damaged.
So, I open the (totally healthy) files in the GIMP first and as soon as 
I save them from there (as TIFF files again), I can open them in Painter.

So, does anyone know what I need to mind when saving tiff files in 
Vuescan so Painter can open them?

greetings
Mu