There is a template file added, which is not accessible by Marvin.
Navigate to your User's home directory and find the chemaxon folder, in which marvin.mytemplates and marvin.templates.properties files are stored.
In these files, you can find some url entries for files used as custom template sets. Check if all files are accessible.
A faster, but blunt solution is to create a backup copy of these files somewhere, delete the originals from your chemaxon folder and try to relaunch MarvinSketch.