FYI all

I have come across another situation that seems to apply to TID 7007172 (known MS bug)

Opening a PPTX file on a remote file server (partial DS-3 routed connection) via Explorer (with Organize|Layout|Details pane enabled) PowerPoint 2007 reports the file as [Read-Only].
Checking Console Monitor File open/lock activity while the file is open Monitor does not show the file as in use by anyone.

To get around this problem with Explorer and PowerPoint PPTX files and the File System either disable Details pane or open the file from within PowerPoint 2007 or save as PPT.

Local network users do not see this problem.