For one reason or another a user I deleted in the admin panel of postnuke still shows up in the Members_List module. However, when I try to remove them there it says the user doesn't exist. Any ideas?

Hum,
Most probably a cache problem.
Have you looked in the users table to see if the user was really deleted ?

palcrypt,

Just a thought, but if you're looking at the forums memberlist, the user would stay there, since the posts will get corrupted if the user doesn't exist. PNphpBB has a separate users table for this reason.

Hope this helps you,
json