Be careful pulling on that little tab! Bend it only enough to slide the clip off...
Not knowing, I bent mine too far in the early days and then every time I used the belt clip after that, I'd find my pager in the grass in my yard.... one time while working on an in-ground pool (which could have turned out much, much worse!)
With guidance from my vendor, I found I could push it back to make it hold a bit better but I just don't trust it anymore...
Now, I just don't use the belt clip.