Strange sorting problem - help?

Ok, I have a simple datagrid (with the XML data isand as part of the page).

The grid loads and looks fine.
Click on "LastName" header. --- sorts fine.
Click on "Date" header - sorts fine.

Here's the problem.

Click on "Last Name" header and IMMEDIATELY click on "Date" header. The grid breaks (no error, just what is displayed is completely wrong and garbaged).

I realize it is probably because when the second sort (Date) is initiated, ithe grid is still in the middle of the first sort (LastName).

Is there a fix that takes care of this happening? Just curious