Bug in File Upload Class?

Make sure the folder and files are writable.

Folders/Files are writeable and upload works fine first time, but if I re-upload and need to write over previous file, I get this error:

"File exists, overwrite is FALSE, could not save over file ./uploads/avatars/temp/1.png"

Even I have this set in config:
$config['overwrite'] = true;

If it matter I run this under WAMP in my Win7 computer ... have not tried on real server yet ...

Any ideas how to make upload / overwrite work ????

/Stefan