It seems to be quite a common problem that when editing page layouts and master pages etc with SharePoint Designer there are synchronisation issues where SPD thinks a file is checked in/out and yet in MOSS this is not the case.
Reading a post on the net it appears that this could be because there is an issue with the SPD Website Cache – which I guess is the local copy of the files. The resolution to this is to simply delete the website cache, which can be found at:
I tried this and it was enough to:
- Close SPD
- Delete the folder within the Websitecache folder which corresponds to the SharePoint site that you are working on
- Open SPD (ignoring the message about unable to open the site)
- Hit refresh
This seemed to do the trick. Perhaps there’s some setting where the cache could be flushed periodically, but for now this should save some confusion.