Thread:Project:Forum/Warning: mkdir() function.mkdir : Permission denied

I was uploading image files to my website when without warning, the script stopped working and I go this message:-

Warning: mkdir [function.mkdir]: Permission denied in /home/wikikoi/public_html/includes/GlobalFunctions.php on line 2176

Warning: wfMkdirParents: failed to mkdir "/home/wikikoi/public_html/images/7/79" mode 511 in /home/wikikoi/public_html/includes/GlobalFunctions.php on line 2179

I had not made any changes to the script when this occured. It will not upload any image files to the site no matter which extension I use .gif, .png, .jpg etc...!

Any solution that will get me back up and running will be greatly appreciated.