Do a safe boot & repair permissions, & try again. ie: Restart the computer whilst holding down the SHIFT key until you see Safe boot option .. choose it. After it has totally started up, use the Go menu > Utilities & find Disk Utility & open, & repair permissions. Then reboot normally.

If no fix then see the tips here Can't launch LW: Bouncing in Dock (click on link). Consider each one until the last. Sometimes the last is the best, but solving the issue is the ideal approach.