I had some trouble installing SP2 on a Sql Server 2005 64-bit cluster for a client, running on Windows 2003 SP2 OS. All other components patched successfully, except Sql Server Service. It is the single component that failed.
The error number on the active node, where I started the install, is error number 11009. The error number on the inactive node is 29527.
At first I thought MSDTC was not setup properly. But that turned out to be not the case. After some googling, we added the startup account to be part of domain admin. I then logged in with startup account, and setup proceeded without any issues. After SP2 was installed, we removed the startup account from the domain admin group, and all was well.
I recall this happened to me once in the past, when I was trying to get SP2 installed in a virtual server environment. I didn’t dig into it then due to time constraint.