Hi you can change the nunber of lookup fields in the Web Application menu at Central Admin.
When you are in the Manage Web APplication section, in the ribbon you have one dropdown menu, where you will see thresold options about lookup allowed in a list.
Regards!
José Quinto Zamora
SharePoint and Search Specialist at SolidQ(
http://www.solidq.com)
MCITP and MCPD in SharePoint 2010
http://blogs.solidq.com/sharepoint