WP can't make a new post (post.php/edit.php 404 error)

I posted this on the WP support boards, got nothing.

First info:

Every time I try to make a new post, when I click "Publish" it goes to:

http://MYURL.com/wp-admin/post.php/edit.php

And there's a 404 error.

I can't post or edit posts, how can I fix this?

Update:

It doesn't have to do with the theme either, it doesn't work with default theme either.

Also, it was working before, for two posts. Then on my third I uploaded an image, clicked "Insert Into Post" however it didn't insert anything, so I clicked "Publish" and then the error happened for the first time.

Now I can't post or edit my posts.

Update:

Okay, I've worked out the error only happens when I have an image in the post.

So, whenever I try to make a post with <img src=""> tag in it instead of going to the regular page when I click Publish it goes to http://MYURL.com/wp-admin/post.php/edit.php and 404s

Update:

Okay, so it's not just image tags. All HTML. No post works if I put HTML in it, I've tried changing themes, disabling plugins, using rich editor and html editor. Nothing fixes it.

--------------------

Can anyone help me out?

 

bump.......

 

This might be a completely stupid reply and Im sorry if it doesnt help, but have you tried re-uploading a fresh copy of wordpress? Originally I was under the impression that it was a permissions error but for most of the wordpres dir you can have 600 permissions on the box.

If you have access to the box its on make sure that all the permissions are linked to your user (normally username used to login to a cpanel or the host site).

 

I'll give it a shot, thanks.

 

Didn't work D:

 

Ok, two more "fixes" which might help.

In your wp-admin folder create a .htaccess file and put in:

<IfModule mod_security.c>
SecFilterEngine Off
</IfModule>

If that doesnt work, try This link

Apart from that Im stumped

 

The first fix worked perfect, thank you.

 

Not to worry at least something I suggested finally works