Comment 2 for bug 1216807

@Zickzackzuck,

This bug and bug #1218093 both arise from same source - Wrong parsing of tag and task paths leading to malformed tuples being saved and read from '~/.config/gtg/gtg.conf'

This is why Re-install and changing the project.xml in ~/.local/share/gtg did not change anything.
Because your backup conf file did not contain such errors, replacing gtg.conf with it made it work again.