Can't add a field via studio

This is a first. I can usually add fields using studio or by entering the metadata in the fields_meta_data table and doing a QRR. 

I am trying to add a Relate field to Campaigns in my production environment (I did it successfully in dev and tst via studio) and nether method works.

Via studio it just hangs with  a red "Loading"

Via metadata the QRR will not prompt for the addition of the field to the _cstm table as it normally does (and it never creates the field) but shows the field in Studio.

I checked all file and directory permissions, all logs... nothing. There is a CSRF attack if the Studio page stays open for a while, but I believe that happens with BWC modules.

Any suggestions on what else I can check or how else I can do this?

thanks,

FrancescaS