Hello Kaju,
Well the "no virus detected" is reassuring.
It could be a different virus causing AST/ALT to have risen - maybe Hep C or maybe just common cold.
It could also be things like Heamochromatisis.
There are many reasons, and often we can't even find a reason.
So for now, there is no need to panic. The chances are you will be cured, but if not, we can retreat. With GT4 this is easy with Viekira+Sof+Ribavirin (this is REDEMPTION-XP trial) and so far (knock on wood) we have 100% success rate.