I have experienced this with Vista Business, Windows 7 Beta, RC1, and RTM. I have network drive on my server mapped to the Z: drive on my Windows PC and I have been running into issues where I can't move, edit, or delete folders and files.
For example, I was using Picasa to edit pictures on the mapped network drive and after I was finished, I closed Picasa and then used Windows Explorer to navigate to the folder the pictures were in. I tried to cut the folder and paste it into another folder, but each time I tried I received an error of "Cannot delete this folder, it is being used by another program". After more than a minute of trying, I closed both of the Windows Explorer windows, opened them back up, and copied the folder to another folder. I then was able to delete the folder in the original location without issue.
I then went to the folder in the new location and for more than 3 minutes tried to rename the folder, but I received the same error over and over again. Even when I closed the windows and opened them again, no dice. Finally after about 4 minutes I was finally able to rename the folder.
The first issue may have been Picasa not releasing the folder in a timely manner, but the second issue I believe may be related to the Indexing done by my server automatically when files are stored on it. I don't understand why it would be that the Indexer on my server would take charge of a file like that, especially on a file server.
I have also seen this issue before on network drives without explanation. Like when I want to delete a folder, but a hidden file is being used by another program so the folder it is in can't be deleted.