Solved. I had to disable "smooth scrolling"
Edit > Preferences > Advanced > General > Smooth Scrolling
I'm using LXDE on a HP510 Laptop, it's onboard graphics chipset is a: Intel Mobile 915GM/GMS/910GML Express Graphics Controller
. I am not using an xorg.conf file, so the settings are just the default autodetect ones I assume.
I've noticed it when scrolling in firefox, and can't seem to get it to do it when scrolling in other applications, but I haven't really used this laptop much since installing the Fedora 12 LXDE spin recently. I'm not sure what information to supply that will help you help me. Here is a screenshot to show what happens.
I dunno what the big black box is, its only visible on the screenshot. I had to bind a script to printscreen to get it to make a screenshot, so its probably something I need to do here to get rid of it?
DATE=`date +%Y-%m-%d\ %H-%M`
import -window root "$HOME/Desktop/screenshot $DATE.png"
I also can't get the touchpad scrolling to work. Or my external monitor without some issues. So I think I will be making an xorg.conf file at some point.