After some serious debugging I am very pleased that pgfSweave works as it should again.
After finishing a few days work on an analysis of how victimisation - in forms of exposure to sexual, physical and psychological abuse - relates to delinquency, I re-ran the complete file. The first run took 866 seconds:
You can now run (pdf)latex on ‘Utsatthet.tex’ user system elapsed 866.325 23.821 1057.047
Subsequent runs took 2 seconds:
You can now run (pdf)latex on ‘Utsatthet.tex’ user system elapsed 2.080 0.056 8.804
And the cache only takes up 1.2 Mb of disk space. That's why I love pgfSweave.