Launching ARMA 2 (dayz mod) through steam - "Performing first time setup"

[Gashed 16]

Every single time I launch Arma 2 operation arrowhead VIA steam the same Performing First Setup window appears, saying "Installing Microsoft DirectX for Windows (Step 1 of 1).

Every. Damn. Time. Even though obviously it's installed already. Wouldn't be a problem - but it takes about 10 minutes each time.

[Thor Erik 3]

Contact BI or ask on the Steam forums? or both?