I recently added a LaCie Mini Rugged external hard drive to my iMac (Snow Leopard) for regular backups. About two weeks later I get a Time Machine Error that the backup disk is not available and backups are not occurring. I click on Select Disk and it comes up None. Then I get a window saying no AirPort wireless device can be found. I hit <Rescan> in response to this and just get the same window. I thought you only need to plug in the LaCie and open the app. What do I need to do?