In essence, your Gateway URI and Dispatcher URI may not be pointing at the same Cognos server. This causes much confusion for Framework Manager and makes it act very strangely. You may even be able to navigate through your Cognos Connections environment from Framework Manager for awhile, only to be kicked out suddenly with yet another blank screen error. Cognos Configuration will not catch this problem either – it will save your misconfigured settings without a problem (note: it will not save your configuration if you attempt to connect your Dispatcher URI to a non-existent Cognos server).
To resolve this, reset your configuration mappings in Cognos Configuration. Once your Gateway URI and Dispatcher URI for external applications settings are corrected, your blank message error should go away and your connection to your Cognos server should be restored. The configuration settings you need to resolve in this case look like this in Cognos Configuration: