I have a friend (or, my x-girlfriend nags about me being a PC-genious:P) and she has problems with starting limewire sometimes.. Sometimes she gets in and can search for songs, but sometimes she needs to re-install the program and start all over... that's not necesary, right?

Nope it shouldnt be.

What happens when she can't start LW (ie does the app start to load then freeze, does nothing happen when she clicks on the LW icon, is the LW icon totally missing....)??

I think it is the app start to load and then freeze.. It's obviously unstable..:P

What version of Java is she using? Some people have had this prob when using 1.6.0_01 & 1.6.0_02. Try this version instead. Use the JRE offline installer & remove any other Java versions before installing this one.
Archive: Download Java 2 Platform Standard Edition (J2SE) 5.0 Update 11

If that doesn't help, delete LW's preferences folder when LW's properly closed. See point 3 here & also point 2 if you've used older versions of LW in the past (there could be a folder in either location).
Fixes for LimeWire
This will kill all of your settings within options, you'll have to go back through afterwards & reset things. If you're not sure of your settings, go through LW's tools > options & write them all down, so that you can reset things later.

If it's still not opening, try changing compatibility (point 5 in the 'fixes' thread).