Back to your problem, it would seem that the Varilight
is a bit sensitive to certain codes. I got round
this by using Prontoedit to create a page of about
six buttons with different codes in and downloading
them into the Pronto. Best to not use codes that
are in operation elsewhere on your system or you
will find that same problem you have already experienced
with your TV volume.

By trying each code with the Varilight I found
some that worked fine. One didn't work at all
and a couple of others needed two presses of the
button to make the Varilight respond, which was
no good at all.