WordPress problem with permalinks after upgrade

If you get error 404 with your permalinks and RSS feed after an upgrade of your WordPress installation to version 2.8.3, it’s worth to check the “Permalinks” section (under the “Settings” tab in the admin panel). Try set it up to “Common”, save changes and then put it back to your previous structure (“Month and name” in my case). This should solve most of current 404 errors after upgrade. If not, check the WordPress support forum.