"The document could not be created“ or „Template not available“ (Shared Documents - new Document - offer)

Behavior:
You receive a message if you want to create a new document in Sharepoint:
"The document could not be created. The required application may not be installed properly, or the template for this document library cannot be opened.“



Solution:
There are problems with the client application. Maybe there are different Versions installed or the installed version is incompatible to the Sharepoint Foundation. E.g. you have installed more Microsoft Word Versions as once or you use an older Microsoft Word Version.