Unable to schedule 'Dominator Tree Construction'?

While I'm building 3.0, I thought I would ask if anyone has seen the following
with TOT:

Unable to schedule 'Dominator Tree Construction' required by 'Module Verifier'
Unable to schedule pass
UNREACHABLE executed at <root>/llvm/lib/VMCore/PassManager.cpp:1223!

This code was working with TOT ~3 weeks ago. This is a code generator, and
execution library (the IR C++ classes and JIT), running on 10.7.2. Simpler JIT
programs work fine, so I'm guessing there is a bug in how I'm laying out the IR
which previously slipped through (given that it is apparently dying in the verifier).
I'll look at line 1223 as soon as I get 3.0 built.

Thanks in advance