External HDD Folders Won't Open Even With Restore Option Checked

Hello,

Recently after booting up I get the error msg that the folder is not accessable. I usually leave a folder or two from my external 'F' drive open when I log off so I can pick up where I left off the next day. But now I get the bong sound and the error msg and have to click on the red X to close out the error msg. Strange thing is, the drive is seen in My Computer and if I click on a desktop folder related to the external drive it will open right up. The problem only happens on start up, not a reboot. The external drive starts right up when I start the pc (desktop) because the drive's power light begins blinking. The problem is not the hard drive. I used another external drive and got the same problem. It's also not the usb port because I've tried other ports with no change. The mouse and keyboard both work fine so I'm figuring it's not a problem with any of the ports. I'm at a total loss on how to solve this problem. Any ideas?