Trackpad not sending mouseUp on tap?

Question

I have a problem with the trackpad on my 17" MBP (2009, unibody). It's not consistent, but it is happening with increasing frequency. I normally have my trackpad set for click on tap (I hate how the whole pad moves for a physical button-click, plus the clicking noise has always driven me bonkers).
Maybe six months ago, I noticed that tap-clicks were not always releasing, like it wasn't always sending a mouseUp event after a tap. It doesn't show as if it were a trackpad drag or a click-and--hold, but I'm not familiar enough with the trackpad drivers to know what it does with a mouseDown-only event on tapping (since a tap-drag or tap-click-and-hold requires two taps), so the behavior may be exactly that.
What actually happens is that it looks like the click didn't register, and when I tap again, it does one of two things. If the cursor hasn't moved since the first tap, it treats it as two separate clicks (not the same as a double-tap, which is a click-and-hold), so if it was clicking on a button, the button reacts as if clicked twice. If the cursor has moved since the first tap, it treats it as if I performed a drag action from the first click location to the second. So if I had, say, clicked in a text field, moved the cursor, then tapped again, it selects the text I've passed over instead of placing the insertion point where I clicked.
Again, this does not happen consistently, and it seems to vary from one app to another. Safari is where it seems to happen the most, but that may be only a perception based on the fact that I spend more time in Safari than any other app. It does not happen with a full physical click (the trackpad-button actually depressing and clicking), only with tap-clicks. It also does not happen with multi-finger taps, only single-finger taps.
My primary question, I guess, would be: does this seem to be more likely to be a software or hardware issue? If it's software, what would I need to patch/replace/update to fix it? If it's hardware, I guess a trip to the Genius Bar would be called for. (The MBP is still under AppleCare, so I'm not concerned about cost, but I don't want to be without a laptop for the duration of a repair cycle.)

Answer 1

Just to clarify, since you didn't specifically mention it: are you absolutely certain your table is 100%, completely total "flat"?  (IOW, use a metal ruler to check.  A wood ruler can bend or bow so you need something that you are 100% confident is true flat.)  Obviously, if the table is not perfectly flat, (i.e.: is bulging up,) then of course that could cause the Trackpad to wobble.  There are two rubber feet on the front of the Magic Trackpad, but the back under the batteries is "solid."  (See the description in second paragraphy in my response here, if you're not sure what I'm talking about.)  So it is more critical to have the table under the battery area of the Trackpad more "flat" than under the front of the Trackpad, but of course any unevenness in the table could cause a wobble..