Thanks for the suggestion, Irene.
The problem doesnt seem to be that I cannot open a data file.
I removed all but one. And that didnt change a thing.
And when I start outlook with 'outlook /safe', so in safe mode, I can work with all data files and I have with no problem with them or the window at all.
But as said, safe mode is limited in functionality and in safe mode all add-ins will not work, nor will a number setting changes be remembered after exiting outlook. Also some registry settings will not be loaded at the start: e.g. I use the ForcePSTPath setting in the registry; in safe mode outlook doesnt seem to input that parameter from the registry, so I need to do a lot of clicking to add data files from my alternate data folder location. But once done, these data files work fine in safe mode.
Which raises my suspicion that the issue I have may be caused by a registry problem. I did clean the registry with ccleaner to see if that would be a medicine, but no it was not what the docter ordered. I did also try to delete my profile in the registry. But that didnt change a thing, except that I had to rebuild my profile from scratch and reconnect all my data files: a nice wasted hour of my time
. (would there be a way to backup a profile from outlook without backing up the whole registry?)