Previous release from fc4 used %define somajor 0 And this version most definitely is not binary-compatible.
Side-issue: I maintain uw-imap in Extras, and already have a libc-client2004g pkg, using somajor 2004g. 2 options: 1. avoid overlap, use something *other* than %%version as somajor 2. If you choose to use 2004g (like how openssl's somajor, that's why I chose it), then make sure to add Obsoletes: libc-client2004g
I've just bumped the somajor to 1; thanks a lot for the report.