Seems to be a webserver problem.

Because, if you remove the value after "redirect_to=" in the URL, it works.
The error gets triggered just by using "redirect_to=http" or any other common protocol like "ftp" or the like.
Probably a mod_security (Apache module) issue, which does not let it through because it might get uses as an injection for a script.

The parameter is used by b2evo to redirect to a certain page, after the user has logged in (in this case).

Try the following:
Add the function to /inc/_misc/_misc.funcs.php:

/**
 * Try to make $url relative to $target_url, if scheme, host, user and pass matches.
 *
 * @param string URL to handle
 * @param string URL where we want to make $url relative to
 * @return string
 */
function url_rel_to_same_host( $url, $target_url )
{
	$parsed_url = parse_url( $url );
	if( empty($parsed_url['scheme']) || empty($parsed_url['host']) )
	{ // no protocol or host information
		return $url;
	}

	$target_url = parse_url( $target_url );
	if( ! empty($target_url['scheme']) && $target_url['scheme'] != $parsed_url['scheme'] )
	{ // scheme/protocol is different
		return $url;
	}
	if( ! empty($target_url['host']) )
	{
		if( empty($target_url['scheme']) || $target_url['host'] != $parsed_url['host'] )
		{ // target has no scheme (but a host) or hosts differ
			return $url;
		}

		if( @$target_url['port'] != @$parsed_url['port'] )
			return $url;
		if( @$target_url['user'] != @$parsed_url['user'] )
			return $url;
		if( @$target_url['pass'] != @$parsed_url['pass'] )
			return $url;
	}

	// We can make the URL relative:
	$r = '';
	if( ! empty($parsed_url['path']) )
		$r .= $parsed_url['path'];
	if( ! empty($parsed_url['query']) )
		$r .= '?'.$parsed_url['query'];
	if( ! empty($parsed_url['fragment']) )
		$r .= '?'.$parsed_url['fragment'];

	return $r;
}

Then in /inc/MODEL/users/_user.func.php replace the get_user_login_link() function with the following one:

/**
 * Template tag: Get link to login
 */
function get_user_login_link( $before = '', $after = '', $link_text = '', $link_title = '#' )
{
	global $htsrv_url, $edited_Blog, $generating_static;

	if( is_logged_in() ) return false;

	if( $link_text == '' ) $link_text = T_('Login...');
	if( $link_title == '#' ) $link_title = T_('Login if you have an account...');

	if( !isset($generating_static) )
	{ // We are not generating a static page here:
		$redirect = regenerate_url();
	}
	elseif( isset($edited_Blog) )
	{ // We are generating a static page
		$redirect = $edited_Blog->get('dynurl');
	}
	else
	{ // We are in a weird situation
		$redirect = '';
	}

	if( ! empty($redirect) )
	{
		$redirect = url_rel_to_same_host( $redirect, $htsrv_url );
		$redirect = '?redirect_to='.rawurlencode($redirect);
	}

	$r = $before;
	$r .= '<a href="'.$htsrv_url.'login.php'.$redirect.'" title="'.$link_title.'">';
	$r .= $link_text;
	$r .= '</a>';
	$r .= $after;
	return $r;
}

This will then always use a relative URL for the redirect_to param, if it can be used (i.e. your $htsrv_url is on the same host as your blog, which is the case here).

This only fixes the "Login..." link. There are a few others (e.g. "Logout"). I will fix them also, if your feedback is positive and then commit it for 1.8.3.

Thank you for your quick response :D

I did as suggested.
At first I got an error message, easily solved by editing the _main.php of my skin. (The normal function has been user_login_link so I had to change that)
I suggest you'll change the get_user_login_link function to user_login_link so that it'll work with the normal skins.

Afer this change I'm able to view the blog, but the login link doesn't appear.

[url=http://www.partyshock.de/kolumneblog/index.php?blog=5]Viewable here[/url]

user_login_link() uses get_user_login_link(). It just echos it out.
So, if you use get_user_login_link() in your skin, add a "echo " in front of it, or use user_login_link() as before.

So, what was the error, which you've tried to solve by changing your _main.php file?

Arr Sorry. I did a editing mistake in the user.func.php. :oops:

Login works fine, thx :D

Fine. So I'll apply the url_rel_to_same_host() function to other places also for 1.9.

I have this same problem with my webhost.

I made the changes like you suggested and it corrected it for Login link like expected.

Can I change the other links myself or should I just wait for an updated version to be available?

It's not a big deal since I'm the only one that uses it, but it'd be great to see it fixed.

It's in our repository for 1.9. You would have to manually change the other functions, like e.g. "user_logout_link()" and "user_admin_link()".

awesome.. the only one I realized that was giving me grief was the email link under posts in the get_msgform_link function so I manually fixed that one for myself until the new version becomes available.

Thanks!

I am having the same exact problem with 1.81-rc I do not want to have to modify my code. What should I request that my hosting provider do to correct this issue.

By the way, I am even having the problem when I click the email icon next to my name on post!