this morning i was using quicksilver [one of my favorite mac apps] and it started crashing over and over upon launching. after some research i found that inside ~/library/Application Support/Quicksilver/Shelves there was a 600 mb history file for the copy/paste utility called QSPasteboardHistory.qsshelf. after deleting that file, quicksilver stopped crashing and started working much faster again.
i would suggest that if quicksilver starts acting up, try deleting this file. it will start to rebuild itself next time you copy something.