7
Yes, I see now that your body stretches out from your header size, even in IE7.
Changing the template for Newbb would certainly be a fix.
But, have you considered changing to CBB? Is there any particular reason you are sticking with Newbb when most Xoopsters have moved to the CBB branch? I know there are valid reasons for staying with Newbb, but you might try CBB which (I believe) does a somewhat more efficient job with template design.
I usually try out 10-20 XOOPS templates in a month, fixed width and variable widths, and have never had a problem with CBB in any of them.