Find and Replace plugins stopped working

I seem to have some sort of bug in my WP setup that affects whatever Find and Replace plugin that I use. (I’ve tried 3 so far, all get an error message).

The WP version is the newest one, and the plugins are all updated. I’ve turned off all of the plugins, except for the find & replace ones, but still getting error message:

“Notice: WP_User->id was called with an argument that is deprecated since version 2.1! Use WP_User->ID instead. in /home/dotorgwe/public_html/elsewhere/wp-includes/functions.php on line 2923

“Notice: load_plugin_textdomain was called with an argument that is deprecated since version 2.7 with no alternative available. in /home/dotorgwe/public_html/elsewhere/wp-includes/functions.php on line 2925”

Then it goes to the page not found page.

If someone has a fix, I’d be very grateful for your input. Thanks in advance!