webjunk

The URL on the submit button is wrong.
In the Contact form 7 plugins directory open includes/classes.php
Around line 109 you will see:
$url = wpcf7_get_request_uri();
change that line to be:
$url = ‘/index.php/’.wpcf7_get_request_uri();

See if that resolves it.

Its putting /kontact/#wpcf7-xxxxxxxxx
and it should be like:
/kontact#wpcf7-xxxxxxxxx

Try disabling permalinks. Then see if it works. Then re-enable permalinks and see if it still works.
Would help if we could see the page.

You will need to edit your theme’s header.php
Too early for me(need my coffee) but you will see a section that includes like:
get_option(‘home’)
and you want to remove that section. It will be just above where wp_list_pages is used. You might need to keep it from excluding the Ome page.

Should always activate one at a time.
Not sure what you mean by “crashed”
Rare by an established recent plugin unless it was making changes to the table.
HW could be but very doubtful because of record locking.
Often I see it when people use old plugins that don’t work with WP 3.

He means to create a template. Single.php is for viewing single posts.
Explained her:
http://codex.wordpress.org/Theme_Development

Is there a reason why you are not using PHP mail?
Have you tried the normal stuff:
Disable Plugins?
Try the default theme?

Are you using a local or remote SMTP?
Does it require authentication?

Try the default theme.
Verify Permissions:
http://codex.wordpress.org/Changing_File_Permissions

From wp-admin Tools -> Export and Tools -> Import the blog over.
You might have to fix links to attachements but search & replace makes that easy