This is the second time it's happened to me now. Basically if you've got some changes you think should be in another branch you shelve those changes (you could create a patch). Switch to the branch you want those changes on and then unshelve. Hey presto, you have a load of changes that weren't in that shelve. In my case I had added image files from another branch I'm working on in there, when I hit revert they went bad to a non-added state just as they would've if I had have been in that branch originally.

There must be a bug with shelve, or the way we handle it. This is in hg.