I'm using the bikeit template from Themeforest which uses the gantry framework. I was setting up K2 when I noticed the add item link not working. Turned off SEF and it worked.
Checked the link with SEF on, and the link it's giving is index2.php?Itemid=176
which 404s, on a whim I took the "2" out and used:
index.php?Itemid=176
which works and it brings up the submit form properly.

I'm not using SH404 (don't even know what it is, but in my searching I noticed several people mentioning this module/plugin/whatever it is)

How can I correct this link?
(joomla 2.5.6)

Hi. Are you using any other SEF extension? The link for adding items is index.php?option=com_k2&view=item&task=add&tmpl=component. With Joomla! SEF URLs enabled you should get something different but not index2.php.

I'm not using any other SEF plugins that I'm aware of unless there was something included with the template. I haven't installed anything myself.

If I do a search for installed items using "sef" as a term, I only get system - sef

If you'd like to see this,
www.han-river-riders.com/

with this demo user:
user: test
password: tester1

the link is under the user menu as a drop down, you'll notice it's formatting it as index2.php

This might also be an issue with the rewrite engine, if I turn that off, I get the url:
index.php/login/submit-a-ride-story

which works fine as well. But I'm not sure why the rewrite engine would be breaking only that one.

Hi. I cannot login to your site. Try to login and then append "?template=atomic" to the URL. If the add item link is displayed correctly then that means that something os wrong woth your template overrides.

Sorry didn't see your reply
I didn't get any answer and the accounts were deleted after a couple days.
Some more testing info:
With SEF urls turned off, it still creates the url:
/index2.php?option=com_k2&view=item&layout=itemform&task=add&Itemid=176

for the menu item, but it works. If I remove the 2 that also works.

Trying the URL:
index2.php?Itemid=176?template=atomic
also doesn't work (with SEF turned on)

according to the admin area, the Link should be created like: index.php?option=com_k2&view=item&layout=itemform&task=add

I have no idea why it's creating index2.php
I have recreated the user:
test
tester1
so you can view the link yourself.

I've tracked this down to an absolute reproduceable error with the module.
If I create a K2 edit item menu item and choose no pre-selected category for it
the menu link is created as:
sitename/alias

if I tell it to use a pre-selected category the link is created as
index2.php?Itemid=190

which fails.

actually even if I tell it to pop up in a new window without navigation it rewrites the URL as such.
basically if i do anything but create the default menu item, the URL is written into the "index2" format.