I've recently had my kitchen floor tiled with 60x60 polished porclain floor tiles. After two weeks 2 tiles have cracked these are tiles that have been cut round external corners. Is this due to the way the tiles have been cut? the tiles are fixed to a solid concrete floor.
Also there seems to be a few tiles that when tapped sound hollow in places will this affect the tiles in the long term?

Can you provide any photo's please, and also do you know what adhesive and grout was used. If there is a hollow sound from some of the tiles, it sounds as though they have been dot and dabbed. The correct method would be a solid bed of adhesive. Do you have underfloor heating?

Yes... Cracking tiles is never good. Could you give a bit more info on the floor? How long was the concrete down for before being tiled? Do you know what adhesives the tiler used? Any under floor heting?

It sounds like the tiler has built the tiles up on adhesive and left voids under them, the tiles have then cracked at their weakest point. If the tiler has used 5 spot, Im afraid you can prob expect more broken tiles.

As Brian J says, it's sounds as if they have possibly ben dot and dabbed, if you register on the forum you'll get more of a response though, we're a friendly bunch.

did the fixer use a trowel with notches in and spread the adhesive all over the floor.

sounds very much like dot and dabbing to me, especially as the checkout cuts have already cracked

Hollow sound could be dot and dab but could also be delamination. If they have cracked at external or re-entrant corners this suggests restraint at the corner which suggests either thermal movement or shrinkage. I would lay odds that if you lift one of the cracked tiles you will find a crack in the substrate.

good call Alan (ajax123)