Ply Gem Window Corporation will not honor warantee, Auburn, Washington

Ply Gem is the supplier of the windows for my home.  I am the original owner.  I bought the home from the builder.  4 years ago, one of my windows failed, so I contacted Ply Gem, as the window has a lifetime warantee.  They  agreed that the window was  covered by the lifetime warantee and came to my home and replaced it.  Now I have two more window that have failed, seal is broken, windows are fogging and growing mold between the panes of glass.  The windows should still be covered by the same lifetime warantee.  This time, however, they refuse to replace the windows.  They are saying that I am not the original owner of the home.  They claim the builder of the home is the original owner and when he sold the house to me it voided the warantee on the windows.  I claim this to be pretty lame and bogus.  This company needs to step up and and stand by their product and warantee!