Error after deleting feeds included in a memetracker

Here's a screenshot of the damage.....which appears to be getting worse.

Here's the use case that creates this problem:

i create a bunch of feeds
like 50
i make a new memetracker
i check those feeds
memetracker runs
i get a memetracker
cool
20 minutes later
i manually run cron
to get some new memes
the system explodes
php errors
memory exhausted
etc.
i go into edit the feed list
and turn off 10 or 20 feeds
i save
i get a php memory exhausted error
when I refresh, the memetracker looks the same

though the edit feed list indicates that the ones I turned off aren't there
unsure what to do
i try to delete the feeds themselves

this has helped "free up" the memetracker
sometimes
but
then I get these errors
when I refresh
meanwhile, the memetracker won't update
so performance problem -> memetracker problem