Are you saying that the pop up keeps coming up or that Limewire keeps re-launching of it's own accord?
If it is the first one that is totally ludicrous and this surely is a fault in Limewire, which if it exists should be corrected... If the second you may have a virus.
Fwiw I use Pro, partly to get rid of ther message which I'm sure I only got when LW opened, and partly because it seems cool to me to put a bit of money into the Limewire development. I also do happen to believe that pro works better ... not twice as well or anything .... just better