Invalid use of l() and url()

I get the same error.

I think this is critical.

Same error here. It's possible to debug, but I still haven't figured it out.

This error is because the Advanced User module is calling url() using the old params... and it's not a very robust url() function so it dies :)

Here's a writeup on the 'Unsupported operand types' error, and what I did to solve it (If you don't want to fix the module, just use the first option listed, it'll let you use the module until they fix it.

I get this same error on my install of advuser.6.x-2.x-dev with patch 1.14.2.3 when I attempt to send mail to multiple users.

If I go to admin/user/user/advuser and try to "Email selected users" I get to the page where I can compose my message. But when I click the "Email" button I get:
Unsupported operand types in (drupal path)/includes/common.inc on line 1376

However, unlike an earlier report, I do not get this error when I try to use the new user registration I also don't get it using the contact form.