Arjo
This is almost certainly a spooling issue. You can get round this by using example 6a in the 'Learn by Example' section of Help.
Basically you set the page length in QI to a smaller size - say 1 metre. When you load the file, answer 'Yes' to 'Span multiple pages'. QI will cut the image into exact 1m chunks, and the 7900 will butt them together perfectly (turn off automatic cutting
).
Brian