mouseup behaves different in firefox and ie

I have some drag features in my aw grid. I click the mouse and drag it. When i let go of the mouse, I highlight the cells. So if I start at row 1 and mouse up on row 4, I highlight those rows. In IE, the onMouseup gives me the row = 4 when I release it. However, in Firefox it gives me the original row (1). Is there a work around for this?

Think I found the answer. Compared my code to the deag and drop in the friends site (Jim Hunter). There was an entry:

#myGrid {-moz-user-select: none}

This seems to resolve the problem. Any feedback why this would do it???