A member of https://lists.ubuntu.com/ told me to rename the hidden home subdirectory .cache to xx.cache and then reboot.
It worked to me but I have lost the history of Unity sidebar and browsers except firefox.
If it doesn't work then he said to try the same with following other subdirectories: .config, .gnome, .gnome2, .gnome_private2, .gconf, .gvfs, .local
Finally, re-rename the subdirectories except the causing one.
A member of https:/ /lists. ubuntu. com/ told me to rename the hidden home subdirectory .cache to xx.cache and then reboot.
It worked to me but I have lost the history of Unity sidebar and browsers except firefox.
If it doesn't work then he said to try the same with following other subdirectories: .config, .gnome, .gnome2, .gnome_private2, .gconf, .gvfs, .local
Finally, re-rename the subdirectories except the causing one.