Some users have experienced issues with Project files getting stuck at check-in. Projects are seen to be ‘Pending Check-in’ when viewed in the Cached list of projects, and when opened they only open in read-only.
It is suspected that this is caused by editing a project file offline and then uploading straight onto the server rather than editing the server generated file created at project startup.
Workaround: Clear the cached list of projects.
1. To do this open project professional / go to Tools / Local Project Cache / Cleanup Cache.
2. Select the problem project from the list under Remove Projects from Cache, and click on Remove from Cache.
3. Then click File / Open and Retrieve the list of all projects from Project Server. Open the project in question, this should allow you to edit the project.
4. Note: you may need to clear the cache each time you want to edit the project.
Assuming that you are using Project Professional 2007, I would also advise installing the following MS Hotfix: 975923, as this resolves some issues related to cached files.