Looks like WinAntivirus Pro 2006 contains Win_Antispyware 2005. Both of these are on the list of rogue/suspect antispyware (click on link). If these products are going to give false positives, they're not much good.
http://www.spywarewarrior.com/rogue_...e.htm#products

Try disabling these & see if LW will install.