i repaired the permissions - still the same problem..
my powerbook G4 isn't the newest (550MHz, 512MB RAM)
usually i'm only running mail or safari paralelly to vectorworks.
but as i said, the problem didn't appear when i was running OS10.2, therefore i think it is a bug under OS10.3..
the general performance-speed hasn't changed between OS10.2 and OS10.3, only that the selection/deselction of numerous objects has become so time-consuming.
it would be helpful to know , if the same problem appears in VW11 as well.. in that case i would consider another solution for this problem instead of purchasing VW11