MOSS 2007 SP2 issues

After Microsoft releases Service Pack 2 for the WSS and MOSS (SharePoint 2007 SP2) I tried to update my Sharepoint environment to SP2.
There are no issues when you update clean environment, but for customized application there are few things you should be aware about.
Error 1:
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[SPDatabaseGbwSequence] [ERROR] Upgrade object too new (build version = 12.0.0.6341, schema version = 2.0.0.0). Current server (build version = 12.0.0.4518, schema version = 3.0.1.0).
When installed SP2 and run Configuration Wizard
This error tells you nothing what relates to the actual problem. You could think that you installed any hotfixes that changed your database schema or content database might be not in right state. I had the same thoughts but this didn't help at all.
The root of the problem lies in other side.
Cause:
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Investigating this issue I found that free SharePoint template from Microsoft cause you such issue, especially GroupBoard. If you have this template installed - that's the problem, because it interacts with the database schema and doesn't allow SharePoint SP2 to be installed.
Solution:
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Uninstall GroupBoard template
Install SharePoint SP2
Install GroupBoard template.
Error 2:
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“Feature '20477d83-8bdb-414e-964b-080637f7d99b' is not installed in this farm, and can not be added to this scope.”

If you get an error during the psconfig phase and you find this entry in the update.log file
“Feature '20477d83-8bdb-414e-964b-080637f7d99b' is not installed in this farm, and can not be added to this scope.”


Cause:
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A timer Job is missing.

Resolution:
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You need to install this feature to be able to proceed with the update.stsadm -o installfeature -name PublishingTimerJobs