My suggestion is to make sure of a couple things
1. In your vbgallery admin the correct server path to the files and user folders are correct.
2. The permissions on the files and user directories under vbgallery directory on the server is set to 777 permissions.
3. If everything above is correct and uploading does not work you could have safe mode set to on on the server which means you need to in maintenance in vbgallery admin turn the safe mode switch to on.