After the release of WordPress 3.1 now there is one more upgrade available WordPress 3.1.1.

This maintenance and security release fixes almost thirty issues in 3.1, including:

  • Fixes for various query and taxonomy edge cases that caused some plugin compatibility issues
  • Fixes for taxonomy and PATHINFO (/index.php/) permalinks
  • Fixes for IIS6 support
  • Performance improvements
  • Some security hardening to media uploads.

I have upgraded my WordPress to 3.1.1 everything is working fine. Have you upgraded your WordPress to 3.1.1 ? If not you can update it directly from dashboard or download it from here . For more information of change log you can refer it here.