I don't think double click has an action behind it. It may be considered to single clicks (eg. first sort down then up). http://www.ventismedia.com/mantis/view.php?id=2467 claims there is (was?) column auto-resize associated with double click.

I can reproduce: http://www.ventismedia.com/mantis/view.php?id=10852

[quote="windcrest77"]On a brand new Win 8 i5 (3rd generation processor) 12 GB machine...

MM Hangs if you accidentally double click a column header when there are over 150,000 tracks in the grid when you really meant to single click to sort the grid. A single click sort still takes about 15 seconds on this machine, but at least it does not "lock up", but when you double click a column header the only thing you can do is kill the process with task manager to release it.[/quote]

Is a double click of the column heading doing anything different than a single click?

On a brand new Win 8 i5 (3rd generation processor) 12 GB machine...

MM Hangs if you accidentally double click a column header when there are over 150,000 tracks in the grid when you really meant to single click to sort the grid. A single click sort still takes about 15 seconds on this machine, but at least it does not "lock up", but when you double click a column header the only thing you can do is kill the process with task manager to release it.