I can't find anything on this in the forums. Whenever I try to send a notification, I get the following error message:

Can't use string ("ARRAY(0xa2294c0)") as an ARRAY ref while "strict refs" in use at lib/MT/App/CMS.pm line 3749.

The notification doesn't get sent, either.

Anybody know what I can do?

Seems to be a known issue with version 3.15

Update to 3.16 to correct the problem.

I have MT 3.16 installed and am getting the same error. Any solutions?

Same error in 3.17. Please help!

Try uploading the /lib/ directory again, making sure all of the older files are overwritten. Also If you were using a version of Movable Type prior to 3.15, and you had installed the plugin version of the fix for this vulnerability, then you need to remove the patch-20050124-mail.spam.pl file from your plugins folder.