Oh , yeah i had that problem too. You gotta go to Sai's misc file and change some of the settings. I can tell you which ones worked for me if you wanna try it again.
There is a more recent problem with sai for some wacom users. Apparently the new driver update doesn't like sai. It's still usable, but the pen lags after about 10 mins so I have to reopen the file sometimes :/
And I only use sai for art because I like the way it looks and its simplicity. I've used paint.net for text in the past but I'm sure there's a better program for it.