Opera default browser complains with "Another user is running this copy of Opera"

Deleted User

Deleted User

I have an Opera set as a default browser. When I try to open URL from external program (like mail client) while I have running Opera I get an error message like:

Another user is running this copy of Opera.
You should install Opera with individual profiles to allow multiple users to run the same copy independently.

If I open the URL from external program when Opera is not running I get URL opened in new tab. In my expectations same should happen when I open URL when Opera is running.

Does anyone know hot to fix this?
Does anyone have Opera which functions as a default browser without problem described?

Few technical specs: Opera 12.17, x86 under Windows 7 starter.