Well, after getting some comments to my blog post I went today to the local dealer with my machine to test whether the board will be happy with 4 identical 1 GB DIMMs.
Long story made short: it isn’t. Obviously it’s the fault of the Asrock mainboard. Bummer.
So I’m stuck with just 3 GB of RAM. Thankfully the dealer took back the second new DIMM! 🙂