I recently upgraded the machines in our office to ID 2015 and immediately experienced "You do not have permission to open this file or file may be in use" error when trying to open any ID file from our network. I checked the forums and saw that this was an issue with other 2015 users so I decided to call Adobe. The first person I talked to couldn't help so she sent me to a their two ID support. This person asked if everything worked locally, which it does, and then she said that it was an issue for my IT department. I told her that the only thing that changed in the last two days was the upgrade to 2015 from 2014. She repeated that it was an IT issue and that this was not a known problem. I told her to check the forums, because it is all over the place. I then reinstalled ID 2014 and, sure enough, no issues at all.
Dear Adobe, explain that. Try being a bit more helpful to your customers. What changed in 2015 that would cause this? Work through the issue with me. Nope, it's not our issue.
I will not be upgrading to 2015 anytime soon.
A good bit of advice is to wait a while before upgrading to a new version. They always have new issues, and most of the critical problems are patched soon after the initial release. The 2015 version of InDesign only been out a week or two, and that is too soon to risk upgrading and potentially upsetting the workflow of your office.