I have the same problem and it started about a week ago. I run Ubuntu 10.10 so it is not an 11.4 upgrade issue as far as I can see. I wonder if it is due to a routine update but I have no evidence that points to that.
I have 4 USB sticks and one is a 32G stick which contains my backups so this is a serious issue for me. As a precaution I am going to move all my data from a last Deja Dup backup over to Mint until this is resolved. My mouse works fine in the usb drive and the 4 sticks work OK with Mint so it is not a hardward issue. I have been working with the forum but have not yet found a solution. One suggestion was to uninstall usbmount which I did. I can now see my sticks but I cannot move any data in or out of them so they are effectively useless. I see an old bug from about 2008 that was very similar and that was solved with an update to the kernel. ** Attachment added: "Screenshot" https://bugs.launchpad.net/ubuntu/+source/linux/+bug/779735/+attachment/2128599/+files/Screenshot.png -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/779735 Title: Natty doesn't detect external USB harddisk drive -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs