I found out that one of my colleagues was using another developers machine and was using his credentials to checkin. This really works if you dont want to be blamed.... but in real life this should not happen. Anyway to work around this problem all we had to do was to go to
C:\Users\[Username]\AppData\Roaming\Subversion\auth\svn.simple
Delete the hexa file in the folder. This will force you to re-enter your credentials the next time you check in.
Hope this helps.
