when you say Computer suddenly decided to refuse to open any
Does this mean that when you right-click one of these files, there is no option to open them with any program.
Or did you mean that these files would not open when double clicked.
If you select and right-click a *.txt file are there any options available.
Whatever the problem, do not turn off automatic updates - many of these updates patch security holes. If one of these updates stopped csv or txt files opening, millions of people would likely know about it!