We purchased our Santana in early 2001. It came with 700x28 wire bead Continental Ultra 2000 tires. After wearing out these tires we decided to switch to the same tire, but in the foldable version. Both versions of these tires were pumped to 120 psi. Our problems were nearly the same as yours and we quickly switched back to the wire bead version.

At 2500 miles we found small cracks between the spokes of the rear Fir rim. It was replaced by Santana but we had to pay for shipping one way. By the end of that first year (5000 miles) we found small cracks between the spokes of the new rear rim. We speculated that the rim may not have been taking the stress of the disc brake. Rather than pay for shipping again, on a rim we didn't trust, we switched to Velocity Dyad rims. With the new rims, we were able to go back to the foldable version of the Ultra 2000. Of course, they no longer make that tire and we are now using wire bead Gatorskins.

Until you are ready to change to a new rim, stick with the wire bead tires.