You can try this...
<mx:LinkButton xmlns:mx="http://www.adobe.com/2006/mxml" render="(Number(data.flag) == 1)?(visible = true):(visible = false)" label="Click Me" />
Try this ans let me know...
Thank you very much Bhasker. I have marked this as correct answer but there is still a problem. When I scroll the datagrid to right and come back, the linkbutton column gets updated every time in a weird way. Suddenly all rows start displaying the link button after scroll and when I release the mouse key it gets back to normal. Probbly because of the the Flex calling udpateDisplayList every time the user changes something on the display.
Are you getting problem with the horizontal scroll bar or the vertical scroll bar..??
Can you share your working code which depicts your problem..So that I can check..