Error: Internal error: cannot convert ElemStruct to int.

Hello,
last week I got a new computer (Windows 7 system) and just tried to run my Comsol models and an error occurs.
Whenever I try to run the study I get the following error:

Error in sweep: The following feature has encoutered a problem

- Fearture: Compile Equations: Frequency Domain (sol1/st1)
-Error: Internal error: cannot convert ElemStruct to int.
-Value: f6
Error in multiphysics compilation.

This happens with all my models (all ran well on the old computer which was also Windows 7 and also Comsol 4.2).

But when I start a the same models from a USB device no error occurs.
I attached a sceenshot of the error message if someone is interested.

Could anybody help me with this problem?

Thanks!
Annika