Hmmm, you don't give much info so let's have a guess.

If Pro's been working in the past but it's suddenly stopped opening...have you updated Java recently? If you've updated to Java 1.6.0_01 then try reinstalling this version.
Java SE Downloads - Previous Release - JDK 5
Use the JRE offline installer & remove your current Java version before you install this one.

Also try deleting LW's preferences folder when LW's properly closed. See point 3 here (also point 2 if you've used much older versions of LW in the past).
Fixes for LimeWire
This will kill all of your settings within options, you'll have to go back through afterwards & reset things.

If that doesn't help, try changing compatibility (point 5 in the 'fixes' thread) or reinstall Pro. Have you added/upgraded/updated any security programs lately?

If you're still stuck, please give us some details.
System details - help us to help you