Form based Authentication Management

Hello,

I have around 20 site collections with the FBA Pack enabled and they all work fine. However I have 1 site collection that the "Choose at least one group/role to add the user to" is blank. There are no groups to chose. It was there at one point as we added users to it in the past. I have disabled and re-enabled the "Form based Authentication Management" feature with no change. Any suggestions?
That's strange. I assume that you have some groups listed under 'People and Groups'? How many?