Are they blowing off the rim (i.e. bead coming unseated and off the rim and the inner tube then blowing) or are they blowing out without coming off the rim?

Campy rims have a bit of a reputation for tightness, so it would be funny if it was the former. If it is then the recommendation for rubino pros migt help as I hae found them quite tight on Campy Mexico rims. Otherwise check all the spoke heads and the rim tape to see if there are any holes or other problems. Might also be worth checking the valve hole for sharp edges.