There is an issue with PunkBuster with 2.60b clients connecting to 2.60b servers. For some reason PB treats the 2.60b client as 'modified' and kicks it from the server. From several forums and websites I've read connecting a 2.60 client to 2.60b server works fine, though. I checked to try and install 2.60 on my computer, but the only ebuild available is for 2.60b. Is it possible to restore the 2.60 ebuild to portage?
Nope. 2.60 has client-side vulnerabilities. It won't be returned to the tree.