swap full? copied lots of text, mtab empty.

Symptoms:
1.) some X11 programs (kwrite, openoffice.org) complain "could not find mime type application/octet-stream"
2.) vi complained a couple times (but not anymore...) "error writing swap file"
3.) df complains "cannot read table of mounted file systems"
4.) kde cant read free disk space in folder properties (any partition at all).
5.) /etc/mtab is empty.
6.) /proc/partitions shows all partitions correctly.
7.) all these symptoms began at the same time.

this all happened after two things: attempting to "emerge -DNatuv world", (which failed -- I don't rememebr why), and after attempting to copy an extremely large amount of text to the clipboard (where is that, btw? the swap file?) which took quite a while...at least 10 minutes.

please advise.

come on, this has to be something simple...