detlep,
I think the problem is that you are not describing the situation very well.
You first mention that you can't open documents, and then mention a certificate error.
Having just looked at the thread, I am as confused as the rest !
Can you clearly describe what the problem is and we can then try and help you.
I can see you mention this :
On Terminal_Server with MS Office and on normal Windows 8 Clients wis MS Office the file is blocking.
and
The problem is the certificate and I must need to solve it.
Can you try and describe exactly what happens a little more clearly please.
What OS does it occur in, which browser, what the error is etc etc
B. Rgds
John