ArchiCAD &/or video card has a dramatic slow down when you open more than one session of Archicad.
Opening the first session and all is fine and everything work great, then as soon as you open another session of archicad trying to pick or move around in archicad is extremely slow. This persists for five to ten minutes then is goes back to normal.
This did seem to happen after the last hotfix.
A bit more information on your operating system and computer specs would help. This information can be added to your signature (in your Profile, link at top of page) for future reference.