You cannot upgrade glibc unless you *really* know what you are doing. That error means you need to recompile the program for your distro. If you don't have the sources, ask the person who did compile it to compile using older libC symbol versions. If they don't know how, or don't understand what you're asking them to do, tell them to talk to TD on freenode, he can be found in the #autopackage channel.
If you're glibc package is broke, you probably need to reinstall the OS, or boot up in "rescue mode" and force the install of the original glibc package.