So I have done several SP2 upgrades. Depending on the size of the farm and number of databases it can take anywhere from 15 minutes to about an hour. Then I decide to upgrade our internal corporate farm. Two hours after I start I get it going but here is the lesson. Always, always, always have a backup plan. That way you can calmly work through the issues without fear of having to roll back.

So, what happened? PSConfig reported that the Upgrade Failed and the log file gave me:

The B2B upgrader timer job failed.

The upgrade log had a better set or diagnostic messages:

Upgrade [SPSearchDatabase Name=SharePoint_WSS_Search Parent=SPDatabaseServiceInstance] failed.
An update conflict has occurred, and you must re-try this action. The object SPSearchDatabase Name=SharePoint_WSS_Search Parent=SPDatabaseServiceInstance is being updated by COMPANY\Service, in the OWSTIMER process, on machine SERVER. View the tracing log for more information about the conflict.
at Microsoft.SharePoint.Administration.SPConfigurationDatabase.StoreObject(SPPersistedObject obj, Boolean storeClassIfNecessary, Boolean ensure)

Most of the blogs indicated that it was a database error or administrative privileges, but that was not the case for me.

I follows through this knowledgebase article http://support.microsoft.com/kb/944267 and it lead me to this one: http://support.microsoft.com/kb/939308/

While I was working through the issue I noticed that the Timer Service on one of the WFEs was stopped. (Which probably lead to the server cache being out of sync.) So I used the article to walk through the cache clearing exercise and the update ran to completion. HTH