I ran into this after some of the KDE4.6beta upgrades, and thought I'd share the solution.
Problem: Trying to "move to trash" any file or directory caused an error box with the message in this thread's subject. This persisted between reboots, and even occurred when I renamed my /home/user directory, though it worked fine for other user accounts (or when I would sudo an app like dolphin)!
Solution: For me turned out to be due to corruption with the .Trash-(uid) directory on one of my NFS shares. I deleted the directory, and all is working perfectly.
Problem: Trying to "move to trash" any file or directory caused an error box with the message in this thread's subject. This persisted between reboots, and even occurred when I renamed my /home/user directory, though it worked fine for other user accounts (or when I would sudo an app like dolphin)!
Solution: For me turned out to be due to corruption with the .Trash-(uid) directory on one of my NFS shares. I deleted the directory, and all is working perfectly.