Problem with special characters in cell.tooltip

Hello.
I'm builing a websight and has encountered an anoying problem. 
I'm using a gridview and and in the "gridviewRowDataBound" I placed this code:
foreach (TableCell cell in e.Row.Cells)
        {
            cell.ToolTip = cell.Text;
        }
the problem is that the tooltip dosn't show some special charactes and since the websight is for swedish users the "Å,Ä,Ö, é" characters is replaced with other special characters and numbers.
If i place a tooltip on a button or other elements the tooltips are displayed properly.

Does anybody know how to fix this.

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