After setting up a new development environment for an existing Sitecore application where all the custom code was retrieved from the source control repository we ran into an issue.
All buttons on sublayouts which should post back to the page where the buttons are sitting - instead go to the layout where the form element is defined.
Neil Pullinger's blog described the same issue and a solution.
We found that the new sitecore install did not have the App_Browser folder and was missing two files from that folder.
After coping files from an existing working development site to the new Sitecore project and it fixed the problem.