Hi Markus,
did you try running the R30 as a single opponent using Arena for a short human-computer test game? Should work... If not, start with trying to solve this.

Now to the pain point: I also face issues running Arena tournaments, where two MessChess engines must be started by the GUI. Especially should one or both engines put a rather high CPU workload, which is true with the R30. Usually first engine fires fine, then the second one fails.

You can test, loading both engines manually. Load the first one as engine#1, then the second as engine#2. Check CPU use. If CPU runs high (100%) for a while, when starting engine#2, most probably you face the same issue as I do. Bad result is easy to check: right click into second engine area, to change engine settings (should display emulation speed and chess computer level). If the window displays no parameter, the MessChess engine did not fire correctly.

Franz's hint not to let Arena restart engines is a must I do apply. But in addition, should you face the above issue:
- set the emulation to sufficient frames skipping (a fixed value is a bit more efficient than default "auto", from CPU load standpoint)
- load first engine manually. Check engine parameters display, should be ok.
- pause first engine emulation to prevent CPU use and freeze GUI protocol activity (this does not hurt Arena)
- load second engine manually. Should work as well, as context is now quite similar to starting a single engine. Check engine parameters display. If not ok, use Arena 'restart' engine then check again.
- disable pause status from the first computer emulation
- reduce both computers' emulation windows to minimize CPU load due to graphic display
- set the tournament accordingly (engine#1 as first participant, #2 as second one)
At least, you should not face any game starting issue. Next game in sequence (if several) as well, if you prevented Arena to restart engine after each game.

nota bene: I use Arena 3.0 (and Win7)

Hope this helps,
Eric