Error applying SP4 on SQL Server 2005 32 bit

SQL Server Setup has encountered the following problem:
[Microsoft][SQL Native Client][SQL Server]Cannot update user instances.
Reason: Cannot start user instance 'FF9C0784-9B79-48' for update.
Error code: 0x3c0c..
To continue, correct the problem, and then run SQL Server Setup again.

Any idea what this means and how to fix it?

I ran below commands

SQLEXPR.exe /qb UPGRADE=SQL_Engine,SQL_Data_Files,Client_Components,Connectivity INSTANCENAME=MSSQLSERVER

and

SQLEXPR.exe /qb UPGRADE=SQL_Engine INSTANCENAME=MSSQLSERVER

Thanks.