Finaly i found the time to test it myself and indeed MP1 is behaving very strange when putting in more than 128.000 images...
I have logged a supportcall for that at Phase One (90262) and they confirmed this:
Hi - the limit in a catalog will be changes and higher on a comming service release of Media PRO.
Thanks
Phase One
I made a movie of the described behaviour, you can see that previews are not generated for the imagase above 128.000 and they are not 'counted' in the catalog fields part of the interface (they are counted in the catalog folders part):
http://dl.dropbox.com/u/25580003/MP1%20strange%20behaviour%20128000%20files%20or%20more.wmvRoelof