Had an issue on my PC at work with a corrupt reiser4 filesystem (still no clue as to why). I managed to repair the FS using RiP-Linux, but not without some data loss. After reviewing lost+found, I found most files related to some HTML cache of Konqueror, but fsck.reiser4 complained about a file that could not be recovered.
After awhile, I tried running emerge to install some new package, and there it was: a broken portage...

The error I got:

!!! Failed to complete portage imports. There are internal modules for !!! portage and failure here indicates that you have a problem with your !!! installation of portage. Please try a rescue portage located in the  !!! portage tree und  ...