Hey all, I have a 2006 Core 2 Duo iMac running the latest version of Lion (10.7.4, as of this writing) and it runs well. There is just one little annoying problem I have run into lately that I haven't solved, despite finding other posts online with the exact same problem. In my System Preferences, under the Mission Control options, the Show Desktop shortcut selector works with any keyboard shortcut I assign to it. However, when I try to assign any mouse button as a shortcut, it does not work at all. The strange thing is, it used to work awhile back, so I'm wondering if some sort of .plist got corrupted or somehow wrongly edited. I did reboot into Safe Mode, and ran a Permissions Repair from there, and I also reset the PMC by unplugging the Mac for a minute. I also ran Preferential Treatment with full permissions for both User and System Preferences, but all the .plist files it checked came up clean. Unfortunately, none of the above worked, hence why I am posting this: if anyone has any suggestions or advice on how to get the mouse shortcut working for Show Desktop again, I'd love to hear it!