More info is needed. What exact version number (down to the decimal) of AE are you using?
What exact version number OS are you using?
Hardware specs, screenshots of your render settings, etc.
If you don't obsess about color spaces and just use the default color space, render out a lossless video file from AE, and use Adobe Media Composer to compress to the XDCam MXF file you need for delivery, life gets a lot less stressful.
Thanks for your answer, but i don't know an Adobe Media Composer, you surely mean Adobe Media Encoder, or not? Anyway i do not find the option for colour space in Media Encoder, so i would be very thankful if you could tell me where to find it.
I meant Adobe Media Encoder. Sorry. I happen to run Avid Media COMPOSER. I use AE & Avid, never mess with color spaces, and things work out well.