Anyone have any experience with Soft-404 errors on non-error pages on Google webmaster?

I'm getting a lot of "Soft-404 (404-like content)" crawl errors in my account. The links all actually work, but google's crawler doesn't seem to like them, which I doubt will do me many favours.
The problem seem to be mostly with one script in particular, which is a redirect script as follows:

<?php $ROOT=$_SERVER['DOCUMENT_ROOT']; include($ROOT."/includes/session.php");
if ($_GET['type']) {
    $type=$_GET['type']; }
else {header("location:/suggest"); exit;}   //added slash after suggest here, dunno what effect it will have.
if ($_GET['done']=='y') {$status='Thanks for '; if ($type=='website') $status.='the feedback';
    else $status.='your submission'; $status.=', it\'s much appreciated!<br/>I\'ll check it out shortly.';};
if ($_GET['id']){
    $id=(int) $_GET['id']; if ($id!=''){ session_unregister('id'); $_SESSION['id']=$id;}
	else $status='Invalid ID number.';
    }

$_SESSION['status']=$status; header("location:/suggest/".$type.".php"); exit;
//changed from "location:/suggest/$type.php" which also works, in thought that it could possibly be the problem ?>

Where the erroneous usage are all the lines of it's standard usage, eg:
http://pinchweb.com/site/suggestfilter.php?type=group&id=5
Also getting soft-404's on the /suggest/link.php and /suggest/website.php pages.

Either my whole website is full of these Soft 404's and it's only crawled through the "suggest" area so far, or there's something particularly wrong with the "suggest" area.

I've read that they often occur when redirecting to the homepage or such when all else fails, which makes me wonder whether the else{ header("loc... line is the problem.

(site's moving host in a day or so, so links might not work)
Any help would be much appreciated.

Do a lot of pages on your site have similar content, use the same redirect script, etc? Google has declared every page of my site that is behind a login wall (content only available to logged in members; guests just see a login box) as Soft 404s.

Yes, quite a few pages look similar, most of the website is templates that are filled in with a DB entry.
But there are also a lot of very similar pages/redirect scripts that don't have Soft-404's but act similarly to this one above.
I wouldn't mind, but apparently the "googlejuice" doesn't get passed to Soft-404 pages.

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