I'm not sure if it's related, but I've noticed that PSD loses track of "some" Subversion connections when you open a Workset with files in the SVN repository. I had 3 program files from my repository in the workset, but only one of them has the Repository status icon showing at the bottom-left of the window.
If I close the file and re-open, the repository icon shows up.
I'm also using the 64-bit version.