Not a lot of info in the original post, so I'm just going to mention ideas...
1. Are the cross member holes chewed, rough, cracked, or otherwise miss-shaped? Napa sells the cross members for about 60 buck each.
2. Were the plastic cups installed in the correct order? I.E. The metal washer and the large bushing go on the arm. The arm then goes through the cross member hole. Then the plastic cup goes on directly against the back of the cross member, followed by the smaller bushing.
3. Is this the passenger side bushing having issues? The passenger side it really close to the exhaust. Was the heat shield installed on that side?
without more info, I'm not sure what else to suggest.