I have just noticed that most of my frequently used documents have a very strange file name. Basically the last version but one has the valid name and the latest has the valid name suffixed by the computer name.
So, my PC name is KenLap10
an example is a file that should be investments.xls
the previous version is named investments.xls
the current version is name investments-KenLap10.XLS
This has happened to about 10 current documents in my data folder but also to about five that I haven't touched for months and you can see by the file size that it hasn't been changed. I might have thought that this was down to my using an ancient version of Office but I have seen it happen to .txt files also.