There are no users in this category. Mail not sent.

Hi.

Thanks for great module.

Unfortunatelly I got issue with this. I can't send any messages to users, because (I'm giving message here):

There are no users in this category. Mail not sent.

I'd created new roles to be sure that my server will push every mail and put 1500 users in every one (my server provider had this limit). Then I got form with Mass Contact categories, where I check what groups should receive mass mail. And then message I wrote is appearing. What should I do??