If you have V-Ray installed, an optional render engine installed as a plug-in, it gets removed from the installed plug-ins when Tentacles is installed. It then needs to be re-added manually in the package manager in Tentacles.
Also, on non-English versions of Windows, Tentacles fails to run from inside trueSpace, giving a message "Unable to launch Tentacles."
The toolbar in Tentacles is looking for the "Program Files" directory, but cannot if it is another language besides English.
You will need to create a folder called "Program Files" and then you will need to manually copy the Tentacles install to this new folder.