I have heard from a few folks over the past weeks who started running into guide download errors on systems that they had made no recent changes to. In one case, the customer rebuilt the machine from scratch only to hit the same error on a brand new system. I found out that there have been some server-side certificate issues in the past month or so that can result in guide download failures with error code 14 or 33 being reported in the application event log. These issues should be corrected now, so if you have been unable to download guide data with error code 14 or 33, please try to launch Media Center and download guide data again and hopefully this issue will be cleared up.
If you are still running into issues, please refer to the Guide Download Errors section of my Update Rollup 2 Troubleshooting Guide for some additional suggested workarounds.