Clearly you're on a Mac owing to your mention of the Option key.
What OS version?
What Photoshop version?
Did Option-drag ever work for you on your current system to select from center?
Have you installed any haxxies/desk accessories that modify your UI operation per keys held down?
As far as I know, the Option / Alt key select from center functionality is still alive and well in all versions of Photoshop. It works for me here. Perhaps someone more familiar with Mac will recognize your specific issue from the answers to the above and comment further.
I'm running OSX and using CS5, the option/alt key works like it should for the shape tool in Photoshop and Illustrator but just not the marquee tool. I've tried updating my software but it didn't work either.
It's entirely up to you whether you want to divulge the specific versions of the software you have. One thing people sometimes find, when they're forthcoming with details, is that there are Photoshop or OS updates they've missed-out on.