Error upon file upload

Upon (manually via ftp) upgrading to 2.2 I’m receiving the following error message when I attempt to upload images inside Manage/Posts:

The uploaded file could not be moved to /wp-content/uploads/2007/06.
Warning: Cannot modify header information – headers already sent by (output started at /wp-admin/admin-functions.php:1965) in /wp-includes/functions.php on line 1348

Things I have tried already:

• Deleting all files except wp-config and completely uploading again
• reuploading admin-functions.php and functions.php
• checking the permissions on the uploads folder and all it’s content
• disabling all plugins

Which leaves me at a bit of loss as how to proceed. I can of course manually upload images to my site via ftp and link manually, but kind of enjoy using the text editor and file manager despite knowing the code.

Any suggestions much appreciated.