Impdp: looks right, but still getting ORA-39087: directory name invalid

Question

This is fairly mysterious, particularly since I've done this many other times without problems.
I created the directory C:\OracleImportTest on the server's filesystem, created a corresponding directory object DP_DIR in Oracle, and granted my user read and write access to it. I've been staring at it and trying different things all morning, but I still get the following results:
C:\test>impdp cgernon/**** DIRECTORY=dp_dir SERVICE_NAME=test1 DUMPFILE=export.dmp LOGFILE=import.log
Import: Release 11.1.0.6.0 - Production on Friday, 27 May, 2011 12:01:08
Copyright (c) 2003, 2007, Oracle.  All rights reserved.
Connected to: Oracle Database 11g Release 11.1.0.6.0 - Production
ORA-39002: invalid operation
ORA-39070: Unable to open the log file.
ORA-39087: directory name DP_DIR is invalid"But Mercurial!" you say, "surely you screwed something up setting up the directory and either it doesn't exist or you don't have access to it!" I would be the first to agree that is the most likely cause of the problem, but performing the following queries to double-check leaves me in a state of complete confusion:
select * from all_directories;
OWNER DIRECTORY_NAME DIRECTORY_PATH
SYS   DP_DIR         C:\OracleImportTest                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
select * from user_tab_privs where table_name = 'DP_DIR';
GRANTEE OWNER TABLE_NAME GRANTOR PRIVILEGE GRANTABLE HIERARCHY
CGERNON SYS   DP_DIR     SYS     READ      NO        NO       
CGERNON SYS   DP_DIR     SYS     WRITE     NO        NO        Does anyone know of any other conditions that can trigger this error, or see anything I'm missing here? I am thoroughly mystified. Thanks!

Answer 1

Good suggestion, but I'm still getting the same error ... using that command, as typed above.
HOWEVER, changing the command as follows works:
impdp cgernon/****@test1 DIRECTORY=dp_dir DUMPFILE=export.dmp LOGFILE=import.logWhich brings up another question. In the past, I've used the SERVICE_NAME option to specify the TNS Name for the database instance I want to connect to. Is that not what this option actually represents? And if not, why was it working for me in the past?
At this point, I guess my original problem is resolved, but if anyone can explain the SERVICE_NAME option to me, I would appreciate it - thanks!