Thanks for replies. For the sake of closure, I can now report (after a *lot* of work isolating the problem) that this was due to sed crashing randomly and unexpectedly during the gcc build since a kernel upgrade from 2.6.11.12 to 2.6.12.*
Go figure; gcc builds fine when running 2.6.11.12 kernel; sed (and sometimes other tools like rm) crashes randomly during build when running newer kernel... (same .config, vanilla untainted kernels) I'm going to chase this down on LKML now. Sorry for the noise Andrew Walrond
