Without knowing anything about your system, nobody can say anything. Sounds like the element library is simply damaged,. you could just delete the respective cache files in your user directory then...
Moving this discussion to the Fireworks Forum.
Its a windows 7 pc - Version 6.1.7601 Service Pack 1 Build 7601
Processor Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz, 2801 Mhz, 4 Core(s), 8 Logical Processor(s)
Installed Physical Memory (RAM) 4.00 GB
I'm not sure where I would locate the respective cache files in my user directory.