Cufón doubling text on IE8

[Óscar]

We've been having this very weird Cufón issue in IE which cause we
haven't been able to adress. I think it's something to do with text
that's hidden and cuffóned.

The problem is that both the cuffoned and normal text are shown (and I
noticed that the tag that is normally used by Cufón is replaced by
<:cufon>). Anyway, this happens in native IE8 (not the "IE8 mode" of
IE9).

A jsfiddle is worth more than a thousand words: http://jsfiddle.net/Osoascam/vqnh3/1/
To test, click on the red circle so that the text moves left (for some
weird reason this only works on FF and IE, but it reproduces the IE8
error, so I can live with that).

Any help would be very appreciated.