I have a problem with my dreambox dm900 multistream function i am trying to watch for example 10 channels from differant devices at the same time, but every time it works correct for one channel, for others I get the same error wich says "tunning... ", please help me to fix this problem.

mrmko,
my reply is a little late for a speedy fix but better late than never.
Sorry, about that, DID you find a fix?

I had a very similar problem NOT on DM Boxes BUT with these new DVB-S2/S2X Tuners on other Receivers.
Slightly different than yours, because at least you get a Signal and then Tuning Failed errors.
I could NOT even get a Signal.!

I tried for 4 weeks to get a Signal and Scan on these new crap DVB-S2/S2X Tuners.
Finally I gave up and have now been told by a Seller after exchanging 5 Boxes, that it's a combination of LNB, Tuner and DiseqC compatibility problem.
So maybe your problem lies here , check it out.

Another Tip would be when you connect the Cable with f-connector at Rear of Box to the Tuner, DONT tighten it too much to MAX.!!
Leave it a little loose, this Helped me in the END.

Anyway I ended up getting a DM900UHD with A Dual Tuner and absolutely NO problem with Signal and DiseqC.
Hope this Helps you
Cheers
AJP