Cognos Error: CAM-AAA-0136

Symptom
Unable to access Contributor

Problem
Logging onto Cognos Connection gives the error CAM-AAA-0136: User is already authenticated in the Namespace.

Cause
Both Series 7 of Planning and Planning 8.3 are installed on the same servers and client PCs. Both versions of the Contributor Client are installed on the individual users PCs. If someone is using one version of Contributor and then opens another browser and tries to log onto the other version then they receive the error. This is due to it already being logged onto the other Namespace.

Environment
Planning 7.3 and Planning 8.3 installed on same PCs.

Solution
Uninstall the oldest version of Planning.