WSS v3 sp1 did not complete, site not available

Lately I wanted to install WSS v3 Service Pack 1. Server farm is very simple: 1 WFE, 1 DB. Should not be too much of a problem, right?

I started the sp1. At step 7 of 8 it seemed to hang. After an hour of no progress, I decided to cancel the installation. Even that failed.

Again I waited for an hour and then ended the process psconfigui manually. Let's try that again... "This service pack has already been installed".

Oh? Well ok. Let's navigate to my updated portal site then. "The schema version (3.0.149.0) of the database... not he expected database schema version (3.1.3.0)". Therefore the site will not be available?!

Ouch. Fortunately we live in the Google ages and I found this: run psconfig -cmd upgrade –force and then start the configuration wizard again. That did it for me.