Gaming Pen pressure not working

[Infinite Zero]

Yesterday I wanted to draw just cause I got nothing else to do and I noticed that pen pressure doesnt work on SAI(which is my favorite) with the Wacom Bamboo tablet

I've googled and looked at the SAI website, Yahoo Answers, and other forums a lot of times yet it didn't help. Also updating drivers didnt work since I had the latest already.
Rebooting with the USB of the tablet plugged in didnt work either.
What could be the problem?

I wanna draw with pen pressure so badly now.