Do you have both Power saving modes enabled? One of theose power saving modes is the System Power Saving available in Settings, Power Saving in 2.3.6. It shows up as 2 power savings icons in the notification area (still haven't found a way to make those disappear?). What this setting does (after investigating it myself when I upgraded) is cut your CPU down to an 800MHz processor straight away instead of a 1200 MHz processor. So yes it appears as scrolling, and especial web browsing is slower. Untick this option and you are back to normal!!
Admittedly it's a bit stunted. If they were going to do this I would have expected a more dynamic cutting back of CPU eg. when it hits 60% 1000MHz then when it hits 40% drop it to 800 etc. but no it's throttles it by 2/3 straight away. Although some apps it does not seem to make a difference but in animated effects it is noticable.
If it is not turned off in your case then I'm not sure what it behind what you are seeing.
