I am having a similar problem except I am trying to import templates I previously have used to setup web galleries and a web home page (using an older version of LR). These are saved as *.lrtemplate. I get the same error message as noted above.
I hopes of circumventing this error message, I have tried pasting these files in various preset folders I have found under C:\users\myname\AppData\roaming\Adobe\lightroom. I have tried the "web galleries" folder, the "web templates\user templates\, and even the slideshow templates folder. Despite inserting these template files into these folders, they fail to appear in my template dropdown when on the web module page. Can someone help?