QTR-Quadtone RIP

I'm getting a thin white line in the top of the print in every print I 
print with qtr. I read the archives, and there were messages about white 
lines in epson 2200. I have only one line, it's located 4 mm from the  
outer edge of  the printed area in A3 print, and 7 mm in A4 print. The 
margins are same in all the prints.
And this happens in every print I made. I don't think it's a clog, as I 
get it in every print in the same point. Do other r1800 users using UC 
inks get this line? In qtr  2.4 I didn't notice this, but now in 2.5. 
Can't remember if I printed good prints in the beginning with 2.5, or 
were these prints with lines my first prints.

thanks
-matti