After you have upgraded to GlassFish 2.1 from previous GlassFish 2.0 release, you need to do one more step to ensure that Admin Console works properly. This is due to issue # 7404 and also explained in detail in the forum
After the upgrade, you will see the following jars under <AS>/lib/install/applications/admingui/adminGUI_war/WEB-INF/lib
%cd /gf2.1/lib/install/applications/admingui/adminGUI_war/WEB-INF/lib/-rw-r--r-- 1 anilam owner 132712 Feb 3 18:13 jsftemplating-dynafaces-0.1-1.0.jar
%ls -l jsftemplating*
-rw-r--r-- 1 anilam owner 422259 Feb 3 18:13 jsftemplating-1.2-SAILFIN.jar
-rw-r--r-- 1 anilam owner 132712 Feb 3 10:34 jsftemplating-dynafaces-0.1.jar
-rw-r--r-- 1 anilam owner 423089 Feb 3 10:34 jsftemplating.jar
You need to perform the following steps to ensure that only 1 copy of the jsftemplating jars exist and with the correct name so that any further upgrade will not run into the same problem.
1. Remove the 2 jsftemplating jars (jsftemplating-dynafaces-0.1.jar, jsftemplating.jar) from previous installation.
% rm -f jsftemplating-dynafaces-0.1.jar, jsftemplating.jar
2. Rename the 2 remaining jsftemplating jars
% mv jsftemplating-dynafaces-0.1-1.0.jar jsftemplating-dynafaces-0.1.jar
% mv jsftemplating-1.2-SAILFIN.jar jsftemplating.jar
3. Ensure there is only 2 jsftemplating jars for your installation.
%ls -l jsftemplating*-rw-r--r-- 1 anilam owner 132712 Feb 3 18:13 jsftemplating-dynafaces-0.1.jar
-rw-r--r-- 1 anilam owner 422259 Feb 3 18:13 jsftemplating.jar
Now, you can restart the server and Admin Console will be fine.