I cannot save text document in any location or any format

I just get a message saying:
C:\Users\harlt\Desktop …
Cannot find file
Check filename and try again
.
I am using a Swedish version of LO. If I open an old document and modify it I can both “Save” and “Save as”.
But all new documents (Writer, Calc, Presentation, etc) all refuse to save.

Just a guess but have you looked at your file system permissions and free media space ?