First, I would try deleting all the phones on the lot. Second, try downloading FFS lot debugger from here:
http://www.moreawesomethanyou.com/smf/index.php?topic=72.0. Third, examine what custom content you may have on the lot because something may be corrupted and a process of elimination is warranted. Otherwise you will need to move the sim to the bin and on to a different lot and delete the old lot. Hope this helps. Happy simming.