Solved! Go to Solution.
See attached screen shots. In essence, it works for me.
You might try running Depends for x64 and see what it is loading:
http://www.dependencywalker.com/
This relates to the comments from ciava.at.
Is there anything special about your server, e.g. are you loading server core or something which is not just the standard software?
Look back at post #6.
The 2 versions of ESRIRegAsm. One is 32 bit and one is 64 bit.
If I were you, I'd run the 64 bit version because it needs to load 64 bit code. Right?
I only have "ArcGIS 10.1 SP1 for Server" installed (see attached screenshot).
If I were you then I'd find the 64 bit version and run it.
How could it possibly matter?
One scenario is that the DLL that you are registering for 64 bit ArcGIS Server that is x64 only. In this case I don't think that a 32 bit process will be able to load it.
I am pretty sure that ESRI expects you to run the 64 bit version. Find it and try it.
try and see http://support.microsoft.com/kb/2480607
Have you seen if there are hot fix like this http://support.citrix.com/article/CTX125419 avalilable for your system?