I just completed an in place upgrade of SharePoint 2007 to SharePoint 2010. What a crazy experience! Just when you think the upgrade was successful, you run into lots of errors! 
It took me quite a few days to iron out all of the issues and spent countless hours searching the Internet to find solutions. Here are just a few of the issues that I ran into, in no particular order. Maybe this can be helpful for others.
Application Event log error: “Load control template file /_controltemplates/TaxonomyPicker.ascx failed”
- Solution: Rename the 14\templates\controltemplates\taxonomypicker.ascx file. It is no longer used and shouldn’t even be there.
- See: Help Wanted: Taxonomy Picker
SharePoint error: Some or all identity references could not be translated
- Don’t use an account name longer than 20 characters
- Don’t delete an account without being sure it’s no longer in use somewhere in SharePoint
- If you need to re-create an account run “stsadm –o migrateuser –oldlogin domain\serviceaccount –newlogin domain\serviceaccount -ignoresidhistory” in order to reconnect the account in SharePoint.
- See Trying to access Configure Service Account in SharePoint 2010 Continue reading Adventures upgrading to SharePoint 2010