When I use the 32-bit Windows client against my auth-mode server I can't get it to connect from the command line. I can work around the problem by not trying to specify a username and password from the command line and then calling db.auth() once the shell starts up. However, I bet this is confusing for users. This is possibly related to SERVER-3238.

PS C:\Program Files\mongodb-win32-x86_64-1.8.1\bin> .\mongo.exe db.mycompany.com:27017/jared_test -u jared -p jared
MongoDB shell version: 1.8.1
connecting to: db.mycompany.com:27017/jared_test
> show collections
jared
system.indexes
system.users
> exit
bye

PS C:\Program Files\mongodb-win32-i386-1.8.1\bin> .\mongo.exe db.mycompany.com:27017/jared_test -u jared -p jared
MongoDB shell version: 1.8.1
Enter password:
connecting to: db.mycompany.com:27017/jared_test
Fri Jun 10 02:17:06 file [jared] doesn't exist
failed to load: jared