Image error(s): Warning: call_user_func_array() [function.call-user-func-array]

I’ve had an issue with inserting/adding images to my blog for some time now, and I’m hoping to get it resolved. I get the following error(s) when I click the picture icon when writing a post.

Warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, ‘media_admin_css’ was given in /home/greg/public_html/blog/wp-includes/plugin.php on line 339.

I’ve tried deleting and re-uploading the wp-includes folder, but that didn’t seem to work. Any ideas of how I might go about fixing this?

Here’s a screenshot of what I’m referring to –> http://s3.amazonaws.com/ember/n4GV0LmMFX3w96bYqkhKiKoaEbDBJ4Oc_m.png