I also used to have 25fps with a single 9600GT card. Now with a second 9600GT in SLI mode, i get the exact same 25fps! :( i'm so pissed off...
I tried everything mentionned in this thread. Still stuck around 25fps. SLI is working great on Crysis demo for instance. That SLI issue should be the priority of bugfixes imho.
I'm using Windows XP pro x64 too. Is there a known x64 issue for SLI with ArmaII ?? :confused: