close thread permission problems

OKay, I created a usergroup I call 'tech support', and this is like a junior moderator group. I put my two tech support people into the tech support usergroup, and in one forum, tech support forum, i want them to be able to close and open threads at will. So I had them buy the options to close and open threads, however when they go to tech support board, they get this error message:

" you are not allowed to close threads on this forum. "

these people are not added on to the forum as moderators - because they wont really be moderating, just closing threads..

What else do i need to do to give them permission to open/close threads on that board?

[CMX_CMGSCCC]

Which option did they buy specifically? and in which Category?

-CMX