RobotStudio Error - "Resource is held by someone else..."

Hello,

I create an empty cell, load a robot, build system from layout and try to run a simple move program. When I write the program from the virtual Flex Pendant, the program runs, but when I try to write it in the RS RAPID Editor and hit Apply Changes to load them to the virtual controller, the following error occurs: Resource is held by someone else...
The detailed error:


I think is a matter of admin stuff... any ideas how to fix this? I am already running RS with administrator rights.

Thanks.