Are you looking for this link ?
Well thank you, I knew I was missing something.
The funny thing is this issue supposed to be only on non-English installations.
But mine is English although i did install it as Dutch the first time, later changed it to English.
Pitty there are no export settings to 1080p50 for e.g. for pc or media player.
Should this not be in the FAQ?
For my french install I changed the presets to be able to have these settings (which I will use when switching from
my HDV camcorder to a full HD one this year).
But you can do export 1080p50 with PREL by exporting AVCHD MP4 H264 1920x1080p : choose MP4 H264 1920p, then select advanced option, you can change frame/s parameter. This is possible independantly from the settings issue solved on the link. I had the info from a chat with Adobe support, and it works in my french install.