I'm having the exactly same problem. I got my disc today from Play.com and I am running a 64 bit Windows 7 RC1 build 7100 and Radeon HD4870X2 with Catalyst 9.6 drivers. All updates installed to Windows and the 1.02 patch to ArmA2. Not running UAC and tried both: anti-virus on and off.
Seems to install OK, but autorun shows Play button grayed and manually starting the game from shortcut doesn't do anything.