You haven't even told us what OS you're using. This is for windows:

Reinstall Java. Use the JRE offline installer & remove your current Java version before installing the new one.
http://java.sun.com/javase/downloads/index.jsp

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

Now reinstall LW & make sure to use the offline installer (not the recommended one). When you reinstall LW, it'll automatically remove your old version.

If that doesn't help, try changing compatibility. That's point 5 in the 'fixes' thread.

If it's still not opening, have you installed/updated any security programs lately? Make sure that LW's on the exceptions/allowed list for any antispyware etc.