WPMU install redirects to main blog after saving post in sub-blog

Hi all,

I’m running WP 3.5 in the MS configuration using sub-domains, with the domain mapping plugin to handle the redirection..
I currently have only 2 blogs…
->main blog
->sub-blog testa.com

what’s happening is when I edit a page in testa.com dashboard, after I hit update, the page gets saved but outputs “You attempted to edit an item that doesn’t exist. Perhaps it was deleted?” but it does in fact save the page. I can hit back in my browser and refresh the edit page and the changes show up… I’ve determined that it is a plugin, Network Activated’ causing the problem, it uses a custom meta box hooked to save_post to save the custom fields…as I said this all seems to work fine but then I get the error I mentioned…

After further investigation (set-up some logging in the wp-admin/post.php file )…
I’ve determined that what it’s trying to do is switch to the previous blog and tries to save the same post again for that blog, which of course doesn’t exist and causes the error. (i’m guessing it’s trying to go through all blogs, but the first one encountered that doesn’t contain the post kills it)…

What I can’t figure out is why this is happening…I can find nothing in the core code that tells it to switch blogs…here is what the logging I implemented outputs..

-> correct post and blog
———–2013-01-08 17:33:40——————
Saving post info for Blog: 200
— In post.php->edit —
post_id: 5
post->ID: 5
post->post_status: publish
————————– END ————————-
-> still correct…
———–2013-01-08 17:33:47——————
Saving post info for Blog: 200
— In post.php -> editpost —
post_id: 5
chk admin referer: 1

———–2013-01-08 17:33:47——————
Saving post info for Blog: 200
— In wpg_save_meta —
post_id: 5
post->ID: 5
post->post_status: publish
————————– END ————————-
post_id after edit_post(): 5
————————– END ————————-
-> now tries to save post 5 on blog 1 (main blog)
———–2013-01-08 17:33:49——————
Saving post info for Blog: 1
— In post.php->edit —
post_id: 5
post->ID:
post->post_status:
————————– END ————————-