I resently found a solution to fix this problem:

DLL error
—————————
Can’t load C:\Program Files (x86)\IK Multimedia\ARC System\ARC.vpa64

If you also got this error message here is the solution:

Howto get ARC System running unter win7 64Bit:
The best way is to just install one of the free Aplications from IKM like Amplitube Free or Sampletank Free. After the installation you can find a file called xxx in the installation folder. In most cases it´s located here: C:\Program Files (x86)\IK Multimedia\Amplitube 3
 Just copy that file info the ARC System installation directory (C:\Program Files (x86)\IK Multimedia\ARC System\) and it should run.