After several weeks of troubles, I am a happy camper again.
Problem: In some folders served by my Qnap, all files were reported to be Read Only on Win7.
Seemed to work on Win XP, but not on Win7.
Word reported simply Read Only while Notepad told me "Another process is using the file".
Logging onthe NAS side did not show any other traffic.
After testing EVERYTHING it turns out that for some reason, if the preview pane is turned on in the File Manager, it will prevent other programs from opening the file for writing.
That is, if you move to a shared folder in the File Browser, and the the Preview turned on, then if you try to open the file you have clicked on, the preview will prevent the file from being opened in write mode.
No lock-file is written on the NAS, and it is an internal Win7-problem that manifests itself as a problem with the folders that are shared.
Might be worth remembering.