This error occurs immediately upon starting Conga Composer and it's caused by the "Lock IP Address" setting being enabled... it needs to be disabled for hosted AppExchange applications.
Issue
You see an error immediately upon starting Conga Composer.
Cause
The Lock IP Address setting is enabled. The setting must be disabled for hosted Salesforce AppExchange applications.
Workaround
To fix the issue:
Go toSalesforce Setup.
Administration Setup.
Security Controls.
Session Settings.
Ensure that the Lock sessions to the IP address from which they originated field is NOT checked.
ClickSave.
IMPORTANT!You must restart all instances of the browser for the setting to take effect.