This sounds like what I ran into when I tried to sub-class HTML::Template.

The core problem was that something like this existed in HTML::Template:

# It's own "new()" method was being called internally. HTML::Template->new()

Call new() on the current package seemed to fix that:

my $pkg = ref $self $pkg->new();

Details are in the bug report:

http://rt.cpan.org/NoAuth/Bug.html?id=14037