I had decided to buy a Lenovo E430 laptop. When it arrived, I noticed immediately that the touchpad was jittery. That is, when I would drag my finger across the touchpad, the mouse cursor would not proceed across the screen in a more or less straight line as expected. Instead, while following more or less in the direction indicated, it would jitter or jump up and down, as though my finger were extremely shaky.
I found that adjusting the touchpad settings (e.g., making it less sensitive) helped but did not fix this problem. I ran a search and found a very long thread, running from May 2011 to more or less the time of this writing, in which many people indicated that they had been experiencing this on other Lenovo laptop computers, including especially the X220.
People seemed to have traced the problem to the X220’s 90-watt (90W) Ultra-Slim AC Adaptor (P/N 41R4538, 2011.32). That, however, was not the model of AC adapter that came with my E430. Mine was a 65W unit, model no. 45N0193 (FRU P/N 45N0194). I confirmed that, as others in that thread had reported, the touchpad functioned normally, without jitter, when I unplugged the power supply and ran on battery power. Moreover, the problem reportedly occurred only when the power supply was charging the machine (i.e., when the battery was low); apparently the touchpad would function normally when the adapter was plugged in, if the battery was at 100%.
There seemed to be a couple of workarounds. I confirmed that, as others reported, there was no jitter if I was running on AC power when the battery was completely removed. There, again, the problem seemed to be limited solely to times when the AC was charging the battery (which was not possible when there was no battery). (Note that, for a few moments after removing the battery and restarting the E430, the system did not respond to the touchpad at all.) But this seemed to be true only within Windows: when I used a bootable USB drive to boot into GParted rather than Windows, the cursor was extremely jittery, even with no battery installed. Also, I confirmed that, even when the battery was charging, the touchpad was not jittery if, meanwhile, I was touching the metal hinge connecting the E430’s display to its base. I was not able to confirm, as someone suggested, that the touchpad stopped being jittery if I plugged the power adapter into an outlet that had nothing else plugged into it. Possibly that solution would have required me to plug the adapter into an entirely different circuit in the residential wiring.
After that very long thread had been underway for about a year, a Lenovo engineer posted a message offering a knowledgebase item with a potential solution. The solution called for flashing the touchpad firmware, using a downloaded firmware update. I had already installed all available updates on the new E430 through Control Panel > Windows Update, but of course those would not include actual firmware updates. So now I went to the Lenovo website, to find out whether perhaps they had also issued updates for the E430. There seemed to be a number of pages of potential interest at that website, but for now, I just focused on things that seemed related to the touchpad. The drivers and software page did not have anything specifically naming the touchpad at the top level. It did have a newly released BIOS update, as well as a mouse driver update more recent than the driver date shown in Control Panel > Device Manager > Mice and other pointing devices > ThinkPad UltraNav Pointing Device > right-click > Properties > Driver tab. Interestingly, Device Manager was not itself inclined to update this driver, even though it was nearly a year old: when I told it to update automatically, it said I already had the most recent driver.
As described in the main post accompanying this one, I installed many updates. At some point, the touchpad jitters went away. I think, but am not certain, that the BIOS update did it. Or at least the problem seemed to have disappeared at this point, when charging a partly drained battery.