Recently I have been suffering from the following error, associated with the DotNetNuke text editor:
A critical error has occurred.
Object reference not set to an instance of an object.
I found that the error was apparent after uploading a new dll file to the bin directory or if the cache on the text editor had expired.
It was my understanding that if a language pack was missing then the default would be used. I therefore drew the conclusion that the error related to a missing English language pack (en-GB).
I started by ensuring that I had a corresponding English (en-GB) language, at this time a simple copy of the default, in each of the App_LocalResources directories associated with the DotNetNuke modules and core functions.
Unfortunately, the file TextEditor.ascx.en-GB.resx, which seemed to be the obvious choice, did not resolve the issue.
As suspected I have now tracked this down to the use of an English language (en-GB) as the default language of choice, whilst not having the appropriate language pack installed.
The file required is called en-GB.xml and it is to be found in the directory
dotnetnuke/Providers/HtmlEditorProviders/Ftb3HtmlEditorProvider/ftb3/Languages
