One more attempt at this very difficult phrase. The problem, of course, is "vigilada". What on earth does (s)he mean by it?

My first comment, just in passing, is that "contradicción vigilada" is not an unprecedented combination of words. It is used by the Cuban writer Reinaldo Arenas (the one Javier Bardem played in the film) in his Otra vez el mar, in a verse passage:

"[...] una ficha y un enemigo,
un proyecto, una sentencia,
una contradicción vigilada"
http://books.google.es/books?id=N28sAQAAMAAJ&q=contradicción...

In the English translation this is rendered as "a watched contradition", which isn't a great help to us:
http://books.google.es/books?id=cqYrAAAAMAAJ&q=contradiction...

In a poetic context it's a phrase that works by evocation and suggestion, but in an essay it seems to call for something a bit more concrete. I suppose one approach would be to assume that this curator is actually quoting Arenas, put "a watched contradiction" in inverted commas and let the poor reader puzzle it out. But as I say, I think we have to try to find something that works in English and somehow expresses what "vigilada" could reasonably be understood to mean.

To say that this contradiction is "watched over" suggests that it is the object of careful attention. I have been turning over possibilities like "closely observed", "keenly scrutinised", but I can't find anything so literal that seems convincing to me in context. So I've taken a sideways step towards the possible connotation of "tense", which does seem to me implicit and does work for me. Whether this is really the connotation on which we should be focusing is impossible to say for sure: a problem "sin salida".

For the rest, there are several possibilities. I'd use "involves" for "comporta", but "entails" or "leads to" or "gives rise to" would be acceptable. And for "sin salida", I'd settle for "insoluble" or (as Robert says) "unresolvable". It's not quite "inescapable" (which means "inevitable"). I like Ciara's "from which there is not escape (or "way out", I would say), but a point against it is that it will give us two successive relatives, with "en el que" following. A one-word solution for "sin salida" is preferable in the context.