The command
echo 0|sudo tee /proc/sys/kernel/yama/ptrace_scope
didn't do the trick for me, so I took a look at the console output
which indicated
/usr/lib/i386-linux-gnu/pkcs11/gnome-keyring-pkcs11.so: /usr/lib/i386-linux->gnu/pkcs11/gnome-keyring-pkcs11.so: cannot open shared object file: No such file or >directory
I googled and found a fix for this error:
[link=http://askubuntu.com/questions/127848/wine-cant-find-gnome-keyring-pkcs11-so]pkcs11
keyring fix found here[/link]
Now I can log in - after using the ptrace command above.
I'm in the same boat, I was getting 3007 errors when authenticating. After trying the ptrace_scope trick, Diablo would lock up on me. I attempted the solution suggested by the above link, and it just gave me a bunch of dependency errors when trying to install gnome-keyring:i386. Specifically, it couldn't resolve libgcr-3-common:i386.
Basically, I'm finding that Ubuntu 12.04 AMD64 is unable to run D3 for me because of network connectivity issues w/ 12.04.