After upgrading to BlogEngine 1.4.0.0 I faced a problem where extensions where not loading and no error messages or exceptions raised by the application.
Sometime when I make a code change online and fire the blog, the application is compiled by the server and an error use to popup that it is not able to convert a string value to integer.
Finally found out why this is happening.
Reason: In the table "be_DataStoreSettings" the application expects the value in Column "ExtensionType" to be "1" instead of "Extension".
The application tries to convert the string value "1" to integer, but since the old value is "Extension" it is unable to convert string to integer and hence extensions are not loading.
Fix: Change all the values from Extension to 1 under the column ExtensionType in the table be_DataStoreSettings and the problem should be solved.