I used to have a Windows Laptop but switched to Mac OS X 10.6.3. My AIPTEK HyperPen 12000U installed fine on my Windows Laptop but it won't on my Mac. It goes as far as the Installation and reaches about 42, then stops and goes back to the start, asking you to click the Install Button once more. I have tried downloading Drivers for my version of Mac for my HyperPen but they do the exact same thing.

SOURCE: Aiptek Hyperpen with ADOBE PHOTOSHOP

This may come a little late but Updating your tablet with the latest drivers. Worked for me..
http://www.aiptek.com/drivers.htm#hp12u

SOURCE: Aiptek Hyperpen with ADOBE PHOTOSHOP

Hi. I`ve founded that Aiptek Doesn`t work at ADOBE Photoshop 64 bit. Everything works fine at 32

SOURCE: Aiptek HyperPen 12000U Graphic Tablet Can It Work

Yes, but you may have to get creative- They do sell it on ebay but it ships from the UK - so including shipping they are about 27- 30 bucks. However - if you search for the adesso cybertablet 12000 replacement they are the same. This tablet has been sold under at least 5 or 6 different brand names, but they are all the same oem product and you may have luck finding a pen under a different brand depending on where you live. See this thread here for additional AKA's alias of this tablet:

http://geekhack.org/showthread.php?t=11693

SOURCE: Aiptek 12000U "Pen Pad" is missing functions/doesn't work in XP

Same problem here. Back in XP we found we could use another manufacturer's drivers (they apparently share some/all of the same internal hardware), but I haven't found any working alternatives yet (I have not tried them all). In 2006 someone posted: "YES! Adesso, Aiptek, Trust, Medion and another company are all distributing the same graphics tablet, just rebranded! So far, Adesso seems to have the most recent driver developments (version 3.09 vs. aiptek's version 3.08), so I used Adesso's (right from their website)."

If you find a solution, please let me know.

I'm also having a big issue with the pen's cursor flickering between two places (vertically-offset from each other, closer and closer together if I move it towards the upper left side of the screen). It doesn't do this in relative mode. Switching back to absolute caused it again, then I repeated the process and now it works, but the pen-area is not set properly, so I'm looking for the extra tabs which let me/us set the rectangle area for absolute mode.

SOURCE: Aiptek HyperPen 12000U: When no contact

Your tablet works like that: the stylus has in it an pressure sensitive sensor that detect how hard you press it on the page and that determines the width of the line drawn while the tablet has an resistive surface that detects the position of the stylus on it.
So if the tablet is still reacting when the stylus is no longer touching anything with its tip then the sensor inside it is faulty - you will need to dismantle the stylus and see if you can fix it.