What you may want to do is backup your SSRS config, uninstall the SSRS instance, install it again (RTM, then SP3, then CU4), then restore your SSRS config. (technet ref: Backup and Restore Operations ...

Note – This book abbreviates SQL Server 2008 Reporting Services as SSRS and SQL Server 2005 Reporting Services as SSRS2K5. New features available in SSRS and not in SSRS2K5 are labeled with “New in ...