Sortable helper in completly wrong position in IE6

Sortable helper in completly wrong position in IE6


First of all, apologies for my 3rd Sortable realted question today but
I'm tearing my hair out trying to work it all out.
I've got most of it working but have just spotted a big problem in
IE6. When I start do drag a portlet the helper seems to jump to an odd
position.
It seems to be related to the scroll position of the page. If the page
is at the top it behaves correctly, but if I move the scrollbar down
200 pixels the helper appears 200 pixels above where it should. 500
pixels down the page and it jumps 500 pixels higher than it should.
Only in IE6!
Does anyone know a solution?