You can try going tools > options > updates > put a dot in the 'beta releases' button > apply > ok. I really can't remember whether this works or not (sorry), I just ignore the nag

Which version of LW are you using now? Are you happy with it? Lots of people have been unhappy with the latest version, so if you like the version that you have now I'd suggest you just ignore the nag & stick with what you have