Version:           3.5.3 (using KDE 3.5.4 Level "a" , unofficial build of SUSE )
Compiler:          Target: i586-suse-linux
OS:                Linux (i686) release 2.6.18-rc4-0-smp

i used to have the extended taskbar panel instead of the standard kicker's taskbar applet. 
i usually place it at the right side in the upper courner, so that i have a list of windows falling down from the upper-right courner of the screen. i set "Length" parameter to 1%, check the "extend length to fit content" checkbox and set width to ~200 pixels. 

after upgrade to kde-3.5.4 this sidebar is now always 100% long when it is vertical (i.e. on right or left side) when the "extend length to fit content" checkbox is checked. 
before it extended its length just to fit the window list.