Why might git log not show history for a moved file, and what can I do about it?

I've renamed a couple of files using git mv, used git stash, had a quick look at HEAD (without changing it) then did git stash pop to get the whole lot back again. My moves had disappeared from the commit list, so I redid them with git rm and the commit message claimed git had spotted the rename was a rename. So I thought no more of it.

But now, post-commit, I can't get at the history of the moved files! Here's what git says about the commit in question:

~/projects% git log --summary
commit de6e9fa2179ae17ec35a5c368d246f19da27f93a
Author: brone
Date:   Wed Dec 8 22:37:54 2010 +0000

    Moved R_DebugUI into runtime

 delete mode 100644 test/R_DebugUI_iOS.h
 delete mode 100644 test/R_DebugUI_iOS.m
 create mode 100644 system/runtime/src/R_DebugUI_iOS.h
 create mode 100644 system/runtime/src/R_DebugUI_iOS.m

 <<snip older commits>>
 ~/projects%

I'm now trying to get the history of one of these moved files, so I can look at an old version, but I don't get anything very useful:

~/projects/system/runtime/src% git log --follow --find-copies-harder -M -C R_DebugUI_iOS.m
commit de6e9fa2179ae17ec35a5c368d246f19da27f93a
Author: brone
Date:   Wed Dec 8 22:37:54 2010 +0000

    Moved R_DebugUI into runtime
~/projects/system/runtime/src% 

(I've also tried it without -M, -C and --find-copies-harder, but to no avail.)

I can get its history under its old name, which stops at the point it was deleted from its old location:

~/projects% git log --summary --follow --find-copies-harder -M -C -- test/R_DebugUI_iOS.m
commit de6e9fa2179ae17ec35a5c368d246f19da27f93a
Author: brone
Date:   Wed Dec 8 22:37:54 2010 +0000

    Moved R_DebugUI into runtime

 delete mode 100644 test/R_DebugUI_iOS.m

commit 32a22d53c27e260714f759ecb3d3864e38b2e87f
Author: brone
Date:   Tue Dec 7 23:52:51 2010 +000