Lightroom 4.1 RC2 on Windows 7 x64
This is really weird - the Library and Develop modules seem to be maintaining different selected photos.
In the grid view, I double-click an image and it goes full-screen. Then I click on Develop, and I'm looking at a completely different photo.
In the Develop view, the only way to select an image that seems to work is to use the filmstrip at the bottom of the screen.
Even stranger, while in Library mode clicking on photos in the filmstrip does not cause them to be displayed. I'm seeing to completely different and disjoint photo selection mechanisms.
I've seen that in the past with other versions of LR. It usually means that your previews database has got messed up. Deleting all previews, previews.db and root-pixels.db, and clearing the acr cache, and then creating new previews solved it for me. It took a day or two (65K previews)