thunderbird-enigmail-debuginfo-1.5.2-3 contains no sources. Maybe the correct build flags are not being applied or the binaries are stripped too early? 1.5.2-2 did not have this problem.
Problem persists in 1.6-2.
Sorry for the delay... thunderbird build system is so ugly... :( Fixed in new version 1.7pre (simpler build system, without thunderbird sources) Will goes in stable branches later (with 1.7 finale).