I can reproduce this. Working on a fix. In the mean time, could you please post any relevant system log messages (see Console app) that occur when you attempt to open the "Environment Variables" preference pane?

13/02/13 11:33:25.682 PM System Preferences[58283] net.hannesschmidt.EnvPane failed to load.
-[__NSDictionaryI toArrayOfEntries]: unrecognized selector sent to instance 0x7fc61940bd20
13/02/13 11:34:44.384 PM CoreServicesUIAgent[58290] Error: qtn_file_apply_to_path error: Read-only file system
13/02/13 11:36:15.469 PM Locum[58294] Connection with distnoted server was invalidated

Hope this helps..Thanks

Ok, that's what I am getting. As a workaround, you can run

mkdir ~/.MacOSX

before opening the preference pane.

Tried that..still facing same issue..
New message..appears on trying to open the pane second time
"Could not load Environment Variables preference pane"

Shoot, yes, I've overlooked something. This should do it:

mkdir -p ~/.MacOSX && cat > ~/.MacOSX/environment.plist <<EOF
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
</dict>
</plist>
EOF

New version with fix will be out soon.

... and restart System Preferences afterwards.

Fixing this revealed another, similar problem: #2