I cannot reproduce it in 10.1. I can test if you can share your data (or part of data).Here is my script:import arcpy
import os
wks = os.getcwd()
arcpy.env.workspace = os.path.join(wks, "joins.gdb")
in_fc = "states_few"
in_id = "geocompID"
join_table = "table1"
join_id = "ID"
join_type = "KEEP_COMMON"
try:
# note the output layer name is states_layer
# use this output layer in subsequent tools
arcpy.MakeFeatureLayer_management(in_fc, "states_layer")
arcpy.AddJoin_management("states_layer", in_id, join_table, join_id, join_type)
arcpy.CopyFeatures_management("states_layer", "states_joined")
print arcpy.GetMessages()
except:
print arcpy.GetMessages(2)