Wordpress 3.2 beta 2 and WordPress 3.1.3 is now available for download. WordPress 3.1.3 is a security update for all previous versions. What’s new in wordpress 3.1.3?
Various security hardening.
Taxonomy query hardening.
Prevent sniffing out user names of non-authors by using canonical redirects.
Media security fixes
Improves file upload security on hosts with dangerous security settings.
Cleans up old WordPress import files if the import does not finish.
Introduce “clickjacking” protection in modern browsers on admin and login pages
Download wordpress 3.1.3
At sites where I updated to version 3.1.3 on all NEW UPLOAD, the resized image in PNG GRAYSCALE mode (grayscale) are created with defects. full of risks.
I administer several sites. and tested the same image that was uploaded to the prior version 3,1.2 without errors and now the image is generated every corrupt only on sites where wordpress has been updated.
Try this WordPress support forum