Version: 1.11.0 (using 4.2.00 (KDE 4.2.0), Kubuntu packages)
OS: Linux (i686) release 2.6.27-12-generic
In 3.5, I never noticed a difference in the composer between scrolling with the mouse or scrolling using the arrow keys/pgup/pgdn. In 4.2, kmail is *significantly* slower scrolling with arrow keys or with other text motion keys. It will sometimes take as much as two seconds to do a PageUp (I know, 2s doesn't sound like much, but it's an eternity when trying to write an email).
I see this both when my load is high and when not. I do not see it when scrolling the text box with the scrollbars using the mouse. I haven't yet seen it in any other applications, either.
Created attachment 31747 [details]
Video of the problem
Thank you for taking the time to report this bug and helping to make KDE better. This particular bug has already been reported and is a duplicate of bug 167583, so it is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally any further discussion regarding the bug should occur in the other report. Feel free to continue to report any other bugs you may find.
*** This bug has been marked as a duplicate of bug 167583 ***