Comment 68 for bug 896158

Did you see my note 9611 (http://bugs.renegadeprojects.com/view.php?id=1547#c9611) ?

Was your sidebar open to to the tab with a completed-and-waiting-to-be-placed building visible, by any chance? That translucent overlay on the sidebar charge anim is a significant source of slowdown unless your sidebar is in system memory as opposed to vram.