No Data after Form POST

[eluser]Unknown[/eluser]
Hey fellow programmers,

the topic of my thread already describes my problem.
To be a little more specific:

I added the "Layout.php" library to get this type of building the view going for me.
Then I also added an .htaccess file wich contains:

Code:

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?/$1 [QSA,L]

to get rid of the index.php thingy in the URL.

Now it try to send a username and a password with POST from an html form.

Code:

<form id="login" action="" method="post">

            <div class="inputwrapper login-alert">
                <div class="alert alert-error">Invalid username or password</div>
            </div>
            <div class="inputwrapper animate1 bounceIn">
                &lt;input type="text" name="username" id="username" placeholder="Enter any username" /&gt;
            </div>
            <div class="inputwrapper animate2 bounceIn">
                &lt;input type="password" name="password" id="password" placeholder="Enter any password" /&gt;
            </div>
            <div class="inputwrapper animate3 bounceIn">
                <button type="submit" name="submit">Sign In</button>
            </div>
            <div class="inputwrapper animate4 bounceIn">
                <div class="pull-right">Not a member? <a href="registration.html">Sign Up</a></div>
                <label>&lt;input type="checkbox" class="remember" name="signin" /&gt; Keep me sign in</label>
            </div>

        &lt;/form&gt;

Neither $_POST['username'] etc. nor is $this->input->post();
(I use Version 2.2 so leaving the brackets from post empty shouldn't be a problem, right?) is filled with any data.

Btw. it worked like 4 hours ago, then I just added some breadcrumb navigation and now my POST doesn't work.

I guess this was already asked 100 times, but none of the solutions I found worked in my case.

Greetings Peytra

EDIT_1:
I found something really strange. The POST works with every username except the one i Test with.

EDIT_2:
Sometimes I just want to dig a deep, black, infinite hole to bury myself in.
The POST data was there. I just var_dumped it at the wrong step.

Have a nice day lads and lass'