MSSQL 2005 SP2 install error 2259 - what gives?

[sherifffruitfly]

Relevant section of install log (all else was successful):

--------------------------------------------------------------------------------
Machine : FREGE
Product : SQL Server Database Services
Error : The installer has encountered an unexpected error.
The error code is 2259. Database: Table(s) Update failed
--------------------------------------------------------------------------------

I'm not the only one with this error:

http://www.google.com/search?source=ig&hl=en&q=microsoft+sql+sp2+2259&btnG=Google+Search

But all is not lost - the most helpful Microsoft folks at least
provided extensive online help with this error:

http://www.microsoft.com/products/ee/transform.aspx?ProdName=Microsoft+SQL+Server&ProdVer=9.00.3042.00&EvtSrc=setup.rll&EvtID=2259&EvtType=darlib%5cviewinstaller.cpp%40ValidateUpgrade%40sqls%3a%3aViewInstaller%3a%3amodify%40x65b

Good job Microsoft, good job.