Hello. I don't know where to report bugs for packages on backports.org, so I'm writing here. libqt4 backpot is built with g++-3.3, so library has c102 ABI. That means, package name should NOT be the same as package name in etch (which uses g++-4.1, so c2 ABI)! Binary packages should be renamed to libqt4*c102, and should Conflict: and Replace: appropriate libqt4* packages, but not Provide: those. Please CC any reply to my e-mail, I'm not subscribed to this list.