Thanks for everybody who advised. I have filed the two bugs under:
[Bug 22813] wine's loader does not check invalid image size [Bug 22812] mt creates corrupted executables
In a nutshell, just before running mt, wine and vista generates very similiar executables (differing by 4 bytes, two about time stamps and two seems to be some padding at the end of the import table?). Then the mt makes the executables invalid (at least under vista and also according to one of you, from win7).
And wine certainly doesn't behave like vista in rejecting the executables and happily loading them...