For just under a year now i’ve been getting a daily mail from the Plesk daily maintenance script titled
Parallels Panel key update deferral notification
With the following in the body of the message.
Unable to update . An error occurred while processing your key. You can try updating it later.
This problem occurs when your license includes add ons for packages which aren’t installed on the system. This most commonly occurs due to the change in licensing of version 10.4 of Plesk. Since Kaspersky Anti Virus (KAV) was introduced into the standard Plesk 10.4 license, everyone’s keys were updated with KAV capability. Unfortunately the license key update handler does not handle the situation where KAV is not installed very well.
The following new microupdates released on 01/02/2012 solve the issue. 10.4 MU#15, 10.2 MU#15, 10.3 MU#17 and 10.0 MU#12.
While the MU solves the issue for KAV specifically, other modules still cause problems for the key handler, for example MagicSpam and the Game server module. Until Parallels can resolve the issue, you can work around the problem by making sure you have packages installed for all the addons you have associated with your license.