There IS a LW Mac section on the forums.
I am guessing you have OSX. You haven't given any details which OS version you are using.

(a) Try deleting your LW prefs folder whilst LW is CLOSED; Deleting LW Preferences folder in OSX

(b) Also do a Safe Boot & repair permissions. Reboot normally. Then try opening LW. SAFE Boot & Repair Permissions

(c) If still problems, see Can't launch LW: Bouncing in Dock (click on link) & also Major Topics for General OSX Help

(d) If still problems then post back these details System details - help us to help you (click on blue link) including your type of mac computer (eg: ibook, imac, macpro, G4, etc).