I am having problems with the shutil.copy2

I am making a backup program but when I use copy2 the time of my destination file is often two seconds newer than my source file. I was immediately aware that (as in previous bugs) the decimals are always incorrect (so I always use int(os.path.getmtime(source)) but i also see that the seconds are one or two of. It happens in about 10% of the files copied.

example of my trace of the check after the copy2 call "shutil.copy2(src,trg)"
rereading the mtime gives a difference of one second where the target is 1 second newer.

23:13:50 Non Copied: d:\MyPython\archief.txt , f:\PythonBackup\d-drive\MyPython\archief.txt (1177881701 == 1177881702) N

hard to believe? I also used os.utime(trg,(t,t)) to try to correct it but it gives the same error

Anybody have the same experience... and how to solve this, just installed python 2.5.1, no help.....