Freeform returning "Disallowed Key Characters" and "Unauthorized Action" Messages

Question

I would like to create a second form on my ExpressionEngine 2.5.2 site using Freeform. We have been using the Freeform module for about a year and a half, but I have recently been experiencing 2 different problems. I'm not sure if the issues are related or not:

Problem 1 - Disallowed Characters

When I go in to my ExpressionEngine control panel and try to add information to a blank field of an entry, when submitting the change, I always receive a message that says "Disallowed Key Characters." Nothing is wrong with the fields I am entering the data into, and there are no unusual characters in the data that I'm entering.

I am able to enter data into a form when pulling up an old form page on our site in my browser [not in my ExpressionEngine control panel].

Problem 2 - Unauthorized Action on New Forms

I created a simple new form where I am only entering a first name and a last name, then clicking submit. On the webpage in a browser, when I fill those two fields then click submit, I get taken to a new page that says "You are not authorized to perform this action". This doesn't make any sense to me and I'm out of troubleshooting ideas.

Here is the very simple form I am using in my html page, and I have created each of the fields in the Freeform module within EE that are listed in my code -

<form class="application-form" action="#">
    {exp:freeform:form collection="Entry Form" return="home/index"}         
    <fieldset>
        <div class="heading">
            <h2>APPLY TO COMPETE</h2>
        </div>
        <div class="row">
            <div class="col">
                <label for="first_name">First Name</label>
                <input type="text" dir="ltr" id="first_name" name="first_name" value="" />
            </div>
            <div class="col">
                <label for="last_name">Last Name</label>
                <input type="text" dir="ltr" id="last_name" name="last_name" value="" />
            </div>
        </div>
        <div class="row">
            <input type="submit" value="submit" />
        </div>
    </fieldset>
    {/exp:freeform:form} 
</form>

Answer 1

1. is usually disallowed character in the url. e.g. in a get parameter, or in a form input name.
2. i don't think you should add the <form> tag yourself, it will be set by freeform, no?