It seems that Facebook’s image servers are having some issues with uploading images, I tried and failed to upload to both friends walls and my own wall. You can see the error message below that pops up if you try and upload a PNG, JPG or GIF so it’s a bigger problem.
Once you click ok the error image only shows for less than a second before it’s hidden from the user, so it took several screenshots to capture the error block shown below.
Are you having the same issue? Do you know if there is there anything that you can do to resolve it locally?