"not a valid MySQL result resource" error on what is a valid query call, I'm racked on this one.

Okay, so I'm no PHP beginner, but this has me stumped.

I log in to the database.

I get my query together (in this instance, it's "SELECT * FROM com_lease, address WHERE address_id=address.id AND rent_per_month > 840 AND rent_per_month < 940", though it's for a search so the query varies)

I run my query.
                  $result = mysql_query($query)
                        or errorReport($query);     //my custom error report function



I check the query results (this specific one returns 27 rows)
                  //See if we have more than one row
                  $num_rows_primary = mysql_num_rows($result);


I make sure we have a result
                  if ( $num_rows_primary > 0 )
                  {

                        $i = 0;

AND THIS IS WHERE IT MESSES UP:::
                        //Run a while loop to put the record ID into an array for later display
                        while ( $row = mysql_fetch_row($result) )
                        {
                              if ( $i == 0 ) $result = array( $i => $row[0] );//These if's and else's are so the array creation works.
                              else
                              {
                                    $tempArray = array( $i => $row[0] );
                                    $primaryRecord = array_merge($primaryRecord, $tempArray);
                              }

                              $i ++;
                        }
                  }

The mysql_fetch_row returns a "Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource" error.

I tried mysql_fetch_array -- same deal. How could this be? This exact same code was working before ... I even tried stripping out the references to the "address" table in the query, but it still hung. Any thoughts would be wholly appreciated,

Thanks
Joe