I've never made paneer, but as noone has answered your query, I'll give it a go. As I understand it, paneer is made in the same way as ricotta, but using lemon juice as the coagulant. No need to boil the milk, in fact you should take it to just below boiling point, turn off the heat, add the lemon juice, stir a little, then let it sit until the curds rise to the surface, about 10 minutes or so. Skim them off into them off into a strainer lined with cheesecloth (I actually use a Chux), leave it to drain, then press it lightly. I suspect your problem was the long cooking of the milk. Best with nonhomogenised milk, UHT milk will not work. If you have raw milk (ie not pasturised) you might want to pasturise first, unless you are very confident about its cleanliness. Try it again, it does work.