Jeffs,
It is not something that you can turn on or off. As long as you have cookies enabled in your browser it should work. Sometimes, however, things can get out of whack in the cookie world.
Try this,

1) Click on Profile and re-submit your profile. You don't have to change anything, just go into profile and click submit modifications.

2) Click on preferences. Click on "delete all cookies". Make sure that save user info is set to yes. Submit preferences.

3) Close your browser and then reopen it.

That should fix it.
Let me know,

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Bill Wood - Webmaster
MercedesShop.com, LLC