I'm going to bump this thread. I have more information that may be of use in this.
I also have been unable to actuate the manual 3d button on the side of the display. Sony support gave me the run around. Here's the interesting thing, though:
1) It works for my co-worker, who is using a 9800GT (for SBS, not framepacking - also on DVI-HDMI adapter).
2) It works on my Viewsonic media box (not 3d capable in the slightest).
3) If I start SBS on my Viewsonic box and then plug in the PC to the same HDMI, I can use SBS, but I can't deactivate it without resetting the monitor.
Clearly this is a design decision based on the flag of the incoming signal. I use a 4890, and am aware it does not support HD3D; I just simply want to use SBS. If anyone is aware of what the flag is that tells the display (possibly any display) that it is connected to the computer, I would like to know. Even better would be anybody able to explicitly tell me how to bypass it. Also: is anyone aware of a service menu code?
I'm willing to engage fully in solving this problem, I'm just hoping someone out here in "the McGyver of TV's" forum has any information I am lacking. Hope to hear soon.