can't upload images

Since, I upgraded from 1.4.0 to 1.4.7, I am not able to upload images for products. When I choose, upload, I select the file from my hard drive, but I got an error saying there was a problem uploading the image.

Any advice on this?

I've tried on different machines, small image sizes, checked permissions on my folders, and I cannot find the source of the issue.

Thank you,