Theme My Login: Sorry, that key does not appear to be valid

While logging in for the first time after doing a password reset, I get the above message.

It doesn’t stop me from logging in and everything works fine, just this message displays.

This only happens when the new password has special characters in it. If the password is just numbers and letters, the message does not appear.

I disabled all plugins except Theme My Login and this still occurs.

When all plugins are disabled, this error does not occur (i.e. using the default WordPress password reset, etc.)

Multiple users are going to need to reset their passwords on this site and will want to use special characters, so how do I fix this?

Thanks in advance.