I get when you open a * .txh file the following error message: a free (GNU) Source Code Editor no longer works
do you have a little bit more information on this?
Which npp version on which operating system.
Can you try the same but npp started with -noPlugin or -noPlugins (depends on the version used) switch?
What is the content of such a .txh file?
What is different in regards to a default setup of npp?