I had earlier reported the IBM TTS engine segfaulting on my home Ubuntu 6 machine; I'm still to fix that problem. Surprizingly though, I tried it on a different Ubuntu 6 machine, and there, installing
sudo apt-get install libstdc++2.10-glibc2.2on top of the regular Ubuntu install was enough to get the TTS working. The segfault on my home machine occurs inside libc, and as best I can tell the two machines have identical libc installs. So on the positive front, it's only my home machine that appears broken; on the negative side, the fact that the breakage is hard to explain and hence fix doesn't inspire confidence in upgrading. Others have reported not having any problems on Edgy -- so the problem is hopefully transitory.