Attempting to login to System Center Virtual Machine Manager 2008 self-service portal may fail with error in the browser (see pic). "This can occur if app pool for SCVMM self-service portal is configured with Allow 32-bit Apps set to "True" in Advanced Settings. By default on a 64-bit machine, the Application pool in IIS 7 has Allow 32-bit Applications setting set to false, however in certain environments the app pool may've Allow 32-bit Applications configured as True. In these cases we'll receive error message as stated above," explains Microsoft in KB2397656.
To resolve » change Allow 32-bit Applications setting to False from True. Perform following steps: Open IIS admin console » Right-click Application pool corresponding to SCVMM and select Advanced settings » Under Advanced settings, select Allow 32-bit Applications setting and change it to False.