Emacs 24.2.1 will not save files sometimes

modify and save a file - message area says it is saved, but status line
indicates still modified.

No error messages anywhere. File NOT saved on disk.

This does not happen with all files - when 24.1 came out I downloaded it
and it happened almost straight away - I was busy at the time, so I just
reverted to my 23.4.1 installation and ignored it, figuring it seemed like
a fairly serious bug and it would be reported and fixed pretty quickly.

This was under WinXP

I got a new machine here at work with Win7 installed and I noticed that
Emacs was now 24.2.1, so I decided to try again - same problem.

So back to 23.4.1 I go.

Change the same file (that would not save under 24.2.1) with 23.4.1 and it
works fine. Try 24.2.1 again - same problem.

The file where I experienced the problem was a Python source code file. I
was quite happily changing a makefile at the same time without any issues -
they were in different directories though. That is about all I can tell you.

Again - absolutely no error messages/dumps or anything. The editor just
sits there saying it saved the file but indicating that the buffer is still
modified.

Regards
Peter