Try to register the component manually.

For SQL2008

Start->Run

regsvr32 "C:\Program Files\Microsoft SQL Server\100\DTS\PipelineComponents\TxUnPivot.dll"

For SQL2005

Start->Run

regsvr32 "C:\Program Files\Microsoft SQL Server\90\DTS\PipelineComponents\TxUnPivot.dll"

Enable "remote proc trans" using sp_configure on all the servers.

Repairing the shared components and then rerunning the service pack worked for me as well