Thank you for your answer,
I am running OrientDB Server v2.0.1 locally. From the Orient.Client I have a download from about a week ago. The AssemblyInfo.cs in Orient.Client\Properties does not really help for the version, but it's date is 30 January 2015.
My guess is that this issue has nothing to do with either OrientDB or Orient.Client, it is just some setting in the Java environment.
For Java I have in \Program Files\Java the subdirectories jre1.8.0_31 and jre7.
I have less experience in Java than I would like to have...