Problem uploading photos

I’m having an intermittent problem loading photos to both my galleries and my blog. I have tried 2 different browsers (Safari and Chrome) and both methods of uploading ( Browser and Flash) and I get the following message:
The uploaded file could not be moved to /home/anncourt/public_html/wp-content/uploads/2011/07.
I have not changed the format of my photo files.
Any guidance would be much appreciated – unfortunately I do not write or understand code.