Airport Base Station keeps losing AirDisk on Mac

I have a problem with my Airport Base Station. I have the newer Gigabit Ethernet version and my Airport Disk keeps disappearing. I had the pre-Gigabit Ethernet Airport Base Station and never had this problem. The disk that I'm using it with is a Western Digital MyBook 500GB. I have it plugged into a USB Hub since I also have a USB Printer plugged into my Base Station. I don't have any problems with the printer disappearing but at least once a day for no reason the Airport Disk disappears and the only way to get it back is by unplugged and plugging in the Airport Base Station once again. Is there any idea what's causing this and how I can correct this? Unfortunately since I do Chronosync backups to this drive and also use it in a sense as a server it is causing a lot of problems.