Thanks everybody for the comments. The part that is cracked is what I THINK you would call a "coupling" (?). It is the threaded part at the end of the hose that screws onto the propane tank, securing the connection.
Jay, I understand about having the grill outside for years. This one has been outside for maybe 4 winters, but this one has been the COLDEST on RECORD for many years. So I'm just going to believe that the cold is what cracked it.
Jack, I'm with ya on the overtightening. But I don't even use a wrench to tighten, just my little old hands!