perhaps the anti-virus software you use is interfering? Is it set to
scan Office files? look for some "Office Add-in" within the A-V
preferences.

Chris Skrimshire wrote:
Possibly as a result of something inadvertantly tinkered with, I find that
each time I save versions of a particular spreadsheet, saved to the same or
different names, there is also created each time another file.

These other files are suffix-less, are of 0 kbytes size and have hexadecimal
number names of the form '8AAF8000' - a different, and rising, number each
Save time. Their presence, or deleting them, seems to have no consequence.

Qué?