Users were reporting that their Windows domain accounts were being locked out.

After much investigation, the following was discovered.

• When you map a drive with Windows 7, it will try to connect to the “mapped drive” with your logged in credidentals.
  ie. DOMAIN\UserID.
• If the server you’re connecting to isn’t part of your domain, it will generate an Authentication error.
• Collect enough of the Authentication errors, and your domain account (ie. DOMAIN\UserID) gets locked out.

The work around is to use a DIFFERENT user account to your domain account.  Better yet, integrate your Samba server into your AD Domain.

Note:
While the issue about was reported by users trying to connect to a Samba server, I’m guessing you could see it with other network devices as well.