dbghelp.dll fails on rebase (on Windows)

So, recently I started getting

REBASE: dbghelp.dll      Rebase failed.  Signed images can not be rebased.
Error: rebase failed with exit code 99!
dmake:  Error code 99, while making 'REBASE'

during postprocess when the build tries to rebase a whole bunch of
dll's.  This is on Windows 7.

The only way out of this is to try to find an older, unsigned version
of dbghelp.dll and put that into solver. But that's not a permanent
solution.

Does anyone else know of a way around this?

Kohei