All errors being displayed

I can’t seem to turn off error reporting on my site no matter what I try. I’ve had to go in to some plugins and manually correct the notices that have been generated (variables not being set and the like) in order to get them to display properly, but then I download the updated version and have to go at it again. Same with some CORE files (eg. Notice: Undefined property: WP_User::$rich_editing in … on the user admin page!).

I’m wondering if it’s being affected by Fantastico, through which I originally installed it over a year ago. The errors only started popping up in the last 2-3 months.

Any help would be appreciated.
Thanks