A user is pulling down usernames from an LDAP and these usernames contain backslashes. This is all fine and good until the user creates a personal space. They can create these and edit the home page (at the time of creation), but after saving the home page the personal space is no longer accessible.
personal space created at: wiki/display/~us%5Csomeguy
trying to access the personal space fails as the browser is bounced to wiki/display/us\someguy
This also breaks if the username contains a forward slash or a plus sign, and probably various other special characters.