Thanks a lot for your answer, it gave me confidence to try again.
I finally could run Philharmonik Miroslav succesfully through jBridge, but there was a problem to solve first: the authorization process of IKMultimedia that leaded jBridge to some errors.
For anyone in the same situation here is what I did to solve the problem:
Before doing the following, a bridged .dll was already created according to jBridge instructions founded here:
The thing is to authorize Philharmonik Miroslav before it runs through jBridge.
In order to do that I pointed Cubase to scan the folder containing the not bridged original .dll
I removed the folder path to the bridged.dll
Closed and started cubase Cubase again
Open Philharmonik Miroslav (it opens with Steinberg VST bridge but gives no sound)
went through the IKMultimedia authorization process
Then I remade the folder path necessary for the jBridge
Opened Cubase and it worked
The only thing ist that it seems to freeze for a little time when I assign a new sound.
Of course I am glad that there is a way and that it works but migrating from Cubase on XP 32bit to Cubase 6 -64 bit on Windows 7 is already a lot of work if you have a lot of plugs to reinstall and reauthorize.
It is really a pitty that the 32-bit plugs not working in 64-bit add even more work!