We were applying service pack 3 for users and found a problem with modified reports. It appears that the service pack corrupts the reports dictionary during the upgrade process. It seems to be more common in a shared reports dictionary environment.
Before applying service pack 3:
1. Make sure you have a copy of your reports dictionary.
2. Export all of your customizations as a package file.
3. If you apply the service pack and you are crashing, delete the reports dictionary.
4. Import the reports package to recreate the reports dictionary.