Hi there.
I’m working on try to solve the input devices that are happening lately on the latest version of Synfig Studio.
Please try to build the development branch I’ve set in the git repository to see if the patch does fix the problem in your system.
The patch does disable all the extended device settings and ensure that the only one input device selected is the core pointer.
Later, once the user wants to use another extended input device he should enable it to screen in the Device Settings dialog.
To test the development branch please do the following:
- In a separated folder (i.e synfig-source) grab the source code:
$ cd synfig-source
$ git clone git://synfig.git.sourceforge.net/gitroot/synfig/synfig
2) Checkout the devel branch: genete_device_settings
$ git branch --track test_device origin/genete_device_settings
$ git pull
3) Follow the build instructions to build the current branch.
4) If everything was ok, the development binaries are installed in the folder where you cloned the source code, so just go there and run it. The system wide synfig binaries are not modified. It will do just a local install if you follow the script at the end of the build instructions. If you are asked to sudo password then you’re not doing it right 
$ cd synfig/install/bin
$ ./synfigstudio
Please report here any fail or success.
Thanks
-G