I use Slackware 14.1 64 bit and several file managers (Dolphin, Konqueror, ...) I use Dolphin for this example.

I use several USB sticks. But when I plugged in an USB stick today, it showed two USB sticks in the left side of the file manager. When I click on the "old" one (which isn't plugged in anymore; it's name is "Fedora...") I get an error (see below). When I click on the "new" one (which is currently plugged in) I get the contents of the old one!

After rebooting the whole PC it is still the same!

EDIT: I use the huge kernel.

What can I do to fix this?

Try deleting those two bookmarks from Dolphin and then inserting and mounting a thumbdrive and let us know what happens.

I can't delete them, only hide.
And that doesn't change a lot.
Now I can access the current USB stick by clicking on the old one. And clicking the new one gets the same error as before.

Try to see if there are several partitions on the usb stick. Please list the contents of the /dev/disk/ inner directories before and after you plug in the stick.

Before:


After:

Have you an entry for /dev/sdb1 in /etc/fstab?

No, I haven't. AFAIK it would be a bad idea to have such an entry because then I had to mount it manually. But maybe I'm wrong about that.

Just for test purposes I added such an entry and mounting manually worked fine.

Not sure if this is related, but it might be a bit (although, since you said it persisted through a reboot, I'm doubtful)... But I actually used a DVD a few weeks ago (I know, right? It'd been several years since I last used one, and that was a Slackware install disc). I had the drive open in konqueror and ejected the drive manually using the eject button on the drive itself. I then replaced that disc with another and tried to access it. I kept getting the folder contents of the previous disc. I then realized that I failed to unmount the drive before ejecting, so I had to close the open processes and then unmount the drive before I could then mount and use the other disc.

Maybe this can be helpful for future occurrences.

As for the fstab entry, I wouldn't use it. I think gezley asked that to verify you didn't have one that was causing this issue. For removable media, I would keep them out of the fstab (except for possibly external harddrives, if you have specific locations you want them mounted).

Your USB stick looks healthy. When you plug it in, it is recognized as device /dev/sdb and it only contains one partition which is sdb1. The problem might be related with what bassmadrigal pointed out. Maybe the previous USB drive is not unmounted properly before you plug in the second one.

Solved by using a different distro.