Color shadow with LS-40 and vuescan

Hi,

I am using vuescan 8.1.12 on linux to scan negatives with a Nikon
LS-40 (Coolscan IV ED). It works in general, but I am getting colored
shadows around edges in the scan. This is especially visible on the
masked border which is supposed to be white for a negative. Those
shadows are aprox. 150 pixels wide in horizontal direction (the
direction of the CCD line) and 50 pixels vertical. On a test scan
with sane the shadows were less obvious but still visible.

To me that looks more like a harware issue. Has anyone else seen a
similar problem? And what could I do about it?

Matthias