As part of our Sharepoint 2010 Implementation support for a Norway based ISV we were trouble shooting Sharepoint 2007 to Sharepoint 2010 upgrade issues.

After the Sharepoint 2007 site has been migrated to Sharepoint 2010, on creating any new site or document library we hit upon a strange issue that said “User Cannot Be Found”  error message. After endless hours of breaking our head we found out the the issues was due to difference in way the user names are handled between classic and claims authentication. Finally we got a break through by updating the Function within the Sharepoint database that reads the user info.No presence information