There will be a Plesk 8.6.0.5 update on servers:
plwin1, plwin2, plwin4, and plwin6
The maintenance window will between 12:00AM to 2:00 AM PST on Saturday Dec 5th and Sunday Dec 6th 2009.
There may be a disruption in service of around 10 to 15 mins within this period.
Alan.