Pro users get email support for their six months-- http://www.limewire.com/english/content/proform.shtml

Pro 4.0.3 installed and ran well here yesterday, so I'd guess a Safe Boot (hold the shift key when starting your machine) and a Repair Permissions (Disk Utility) should be your first steps. Pro support will probably tell you to trash the LimeWire Preferences (in your Home/Library/Preferences ) and install a fresh version.

You might also want to clean out your Incomplete folder: sometimes too many files there can cause start-up delays.