We've just performed a manual upgrade from 1.8.1 to 1.9.2 and thought everything had gone alright. The frontend seems properly with pages and products and loading fine.
But, the backend is messed up. The pages aren't loading properly. I can see the header and footers, but didn't find the content in between.
I have already flushed the caches but didn't change.
Find the following images for what I mean.
As you can see there is no content showing. The dashboard page shows correctly and the configuration page loads too, but pages like products, orders cache, index etc don't show properly.