If you use Antigen/ForeFront Security and you are using any of these engines: AhnLab, CA, Sophos and also SpamCure, then you must read the post that the ForeFront Team published. Basically, those ones won't be longer updated as explained below:
The AhnLab, CA, and Sophos engines will be retired on Dec. 1, 2009. After December 1st, customers will not receive any updates for these retired engines. In order to make sure your Antigen and Forefront products continue to scan efficiently and effectively for malware, any customers running the AhnLab, CA, or Sophos engines must DISABLE these engines before Dec. 1, 2009 and select from the new set of five engines - Authentium, Kaspersky, Microsoft, Norman, and VirusBuster.