So I've had the issue where my tablet, an Intuos Pen and Touch Small, lagged horribly in Paint Tool Sai, lost pressure sensitivity, and if I tried Photoshop it would work for all of five minutes before going straight lines only on me.
here's how to fix it: DO NOT UPDATE TO THE NEWEST DRIVER.
Uninstall the driver, reboot computer for a clean install of driver. Go to Wacom, go to Legacy Drivers and download the previous driver, make sure you go into preferences and turn OFF Windows Ink if you're using Windows . Something in the new driver has completely messed up the tablet driver apparently.
this is just how I ended up fixing it.
http://viziblr.com/news/2011/8/13/fix-my-pen-makes-your-wacom-tablet-just-work-on-windows-7.html have you tried this? it fixes all the issues the tablet has when butting against the default tabletPC software/
https://shanemarksanimation.wordpress.com/2011/01/27/fixing-pen-tablet-stroke-lag-in-photoshop-or-other-apps-in-windows-7/ have you also tried this -i just found this after my tablet started messing up again-
Link
LucidDP
I've been reinstalling old driver and restarting over and over but it still lags (windows ink turned off) this is driving me crazy. I do work for a game site and have work due tomorrow and I can't do anything about it. Ugh. I'll try again but at least it brings me comfort to know I'm not the only one dealing with this problem.