Version: (using KDE 4.0.0) Installed from: MS Windows Binaries OS: MS Windows Summary says it all. Since all KDE applications as well as Qt Designer suffer from this problem, but no non-Qt applications, I assume this is a Qt bug.
I can confirm that. Though, i guess this behaviour won't be fixed. At least it's not KDE bug, but the Qt behaviour. For you i suggest to fix the msstyle yourself. Get the StyleBuilder (or any other program to edit the msstyle files) and edit the gripper's property "BgType" to be of value "None" instead of "ImageFile". This will smoothly hide the gripper. Note that there're types of them (horiz + vertical for taskbar and for everything else).
Scrollbars are rendered by Qt classes. If this bug is still visible with Qt version 4.7, please report to Qt developers at Nokia via https://bugreports.qt.nokia.com/secure/Dashboard.jspa