Macintosh Snow Leopard: Terminal Problem

I've been having trouble and problems for a while, due to the fact that my Terminal does not work properly. When ever it's opened, I get this strange error that I haven't been able to find the cause of such.

login: illegal option -- D
usage: login [-pq] [-h hostname] [username]
login -f [-lpq] [-h hostname] [username [prog [arg ...]]]

[Process completed]

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It does not allow me to access the Terminal afterwards, because it cancels out the ability to type into it. This happens on any program using a console or Terminal. Help?

I have a Macintosh OSX 10.6.4: Snow Leopard

Metal said:

I have a Macintosh OSX 10.6.11: Snow Leopard

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Are you certain of that? Snow Leopard is only up to 10.6.4 at the moment, with 10.6.5 on the horizon. The only version of OS X that has made it to 10.x.11 is Tiger (10.4).

Oh I'm sorry. My bad.

The error seems to indicate an issue with your user's profile. Try booting to single user mode after creating a new user. Compare that user's profile to yours and find out where the -D flag was set.

Could you dumb what you said down a bit? I'm not very good, nor am I a fan of, Macs.

Still confused. Help? Bumping up topic.

Most of what you'd need to do would require terminal. Anyway try this - open terminal - then go to the Terminal Pulldown -> Preferences -> Startup -> Shell opens with command -> set it to /bin/bash and see if it will start.

Nothing happened. It still shows the same message.

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Let it do its thing - to check your disk
When it is finished checking your disk - click on Parameters -> finder -> show hiddden files and folders
Open Finder then go to your home directory. You will see a whole pile of more files - they should all begin with a . (that's a dot which connotes hidden files in unix worlds)
Make a temp directory and move all those hidden files into that temp directory.
Start up terminal
If that works - then you can use grep to search through those hidden files for this -D option.

Still, nothing happened. Someone help?

Have you tried calling Apple?

No I have not. I was actually hoping someone here could help be get this fixed.