CVS does not notice that a file has changed if the time stamp stays the same

[J. Davison de St. Germain]

Hi,
 CVS does not notice ('cvs diff' and 'cvs update' do nothing) if a file 
changes but the timestamp stays the same.  This is happening to me under 
cygwin cvs on Windows XP.  Specifically I have an image under cvs 
control.  I load that image in google's picasa, and change the caption.  
If I do an ls -l on the image file, I can see that the file size has 
changed, but when I do a 'cvs diff' or a 'cvs update' nothing happens.  
I realize that picasa should change the timestamp, but it doesn't.  And 
there are several other ways that a file could be changed but still have 
the same timestamp.  (BTW, if I 'touch' the file (thus just changing its 
timestamp, then 'cvs diff' or 'cvs update' will then notice.)  How can I 
force CVS to try harder to determine if the file has changed (perhaps at 
least seeing that the size of the file is different)?  I've googled and 
googled to try to find an answer to this, but the closest I've come is 
to a subversion discussion on it... however, to the best of my knowledge 
(I tried it) subversion also does not handle this case correctly.  Any 
help would be greatly appreciated.  If you could copy me 
(dav@cs.utah.edu) on any response, I would also be very thankful.

       Sincerely,
             J. Davison de St. Germain