Error when refreshing page after reapplying sort

I'm attempting to resort the grid after a user has entered data in a new row. In the onSelectedRowsChanging event, I can reapply the sort to resort the grid.

However when I attempt to refresh the page using F5, I get the error message:

'undefined' is null or not an object

I've traced this error message back to the AW.detachEvent in ie.js, but I have no idea what's causing it. Any suggestions??

Thanks in advance