Maybe your computer's infected.
Are you also not able to access LW's tools > options? Sometimes that problem goes along with the popping up thing.

Have a look at the thread below for a few different fixes to try. If nothing helps, there are links to sites that offer specialised help for malware issues
http://www.gnutellaforums.com/genera...s-options.html

If you can't access LW's options either, download AVG Free AV. Update AVG & then scan your computer. There's a link for download in the thread below.
http://www.gnutellaforums.com/downlo...s-options.html