Where is LDFS located and how do I turn it off?
LFDS is the Laserfiche Directory Service and if it's turned off you wouldn't be able to log into Forms.
That... seems to be a very bad error message, with very little info on what is actually going wrong.
I know this isn't much help, Sorry.
When you are on the server running your forms instance, you can go to http://localhost/FormsConfig and then to the "User Authentication" tab. Which is where this is configured. There are options for "Use a Laserfiche Directory Server for Single Sign-On authentication" and "Use Laserfiche Server authentication". You probably have that set to the option for "Laserfiche Directory Server".
To add to this: LFDS (Laserfiche Directory Server) is the recommended way to authenticate, and in some systems required, so I recommend you leave the option in the Forms Configuration selected.
Can you share what you were trying to do when you receive this error? (Go directly to a specific form? Follow a link from an email? Go to the Forms login page?)
I will find out if the behavior here can be improved -- for example, redirecting you to the login page that this option refers to.