Could anyone help me with Sandboxie problems?

I have downloaded Sandboxie at https://www.sandboxie.com/

For several months the program served me well – I ran Firefox sandboxed always.

Suddenly, the program stopped working. I downloaded SandboxiePlus, but it did not work. It is impossible to uninstall SandboxiePlus.

Could it be that AVG Internet Security is responsible for the new problems?