Edit: After half day, my wife’s Mac started having the same problem. I have then applied the solution that I found in the Apple
JaJa Pressure Sensitive Stylus for iPad Review
As the name suggests, among all the thousands of applications an iPad can support, one of the great things about it is that it can also act as a notepad which, simple as it is, is actually a very useful tool to have. But a notepad is useless if you do not have anything to write on it with and while you could use a marker pen, you would ruin a perfectly good tablet display. Fortunately there are other accessories out there that can emulate the power of the pen so you can write on your iPad without damaging it. The JaJa Pressure Sensitive Stylus is a great example of one and intriguingly it relies on ultrasonic noises rather than Bluetooth. It works rather well.
Since it carries out the function of a pen and should be used like a pen, it is only natural that the stylus looks like a pen and is shaped accordingly. This makes it comfortable to hold and use and consequently easy to write with. The tip works in much the same way, although it has a plastic pad on the end, which is transparent for added accuracy, although visually it may take some getting used to.
One of the great things about it is that Bluetooth is not needed to connect it. However, what you may not like so much is the calibration process that needs to be a carried out every time you use it and it does not always work well every time. This is done by first holding the stylus up and press a button to confirm the lack of pressure. Next you have to push it onto a surface and hold a button down to register this new pressure. How well you do this will affect how effectively it will work so you’ll need to take care, especially when pushing against the iPad screen.
As for the actual performance, this depends on how well you calibrated it, but if you do this properly then it really is a great stylus. Comfortable to use and very accurate, it just seems a pity that the calibration is not saved when you manage a good sensitivity range. In addition to this, the calibration sensitivity also reacts differently with various apps- some can pick it up perfectly while others will fail to register it.
If you don’t want to mess around with Bluetooth then this really is your only option but it is potentially a great one. Unfortunately it is too inconsistent to be considered a must-have accessory. However, when it is good, it is very, very good and if you can get the hang of the calibration process you shouldn’t have too many problems. It is also more affordable than many of its rivals so if you are on a budget it might be worth a look. The JaJa Pressure Sensitive Stylus may not be for everybody but it might turn out to be just what you are looking for.