HTTP 400 error on OWA and outlook for shared mailbox

I have a few problems after I switched from windows integrated OWA login to SSL form based.
One computer is constantly having issue to force OWA users to sign in every 5-10 minutes.
The other computer shows http 400 after login id and password were typed no matter who logins into the computer.

The other question is regarding sharing mailbox.
I usually share mailbox  and go to outlook/tool/email accounts, then add it as additional mailbox. this worked well if the inbox has only several subfolders. But now I have one user who has '150' subfolders under inbox. As far as I know, each subfolder has to be configured for sharing and permission to give. Is there any other way simple. Just share the root mailbox and when I hook it upto the other user's outlook, it shows all subfolders of the mailbox?
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crcsupportAuthor Commented:
I resolved the 2nd problem I described above, sharing mailbox. I was able to give full mailbox permission under AD which modified permissions on all subfolders automatically instead of going through in Outlook.

I am still doing research on the first issue 'HTTP 400'. It seems like certificate issue because the computer's IE keeps popping up certificate warning when I browse internet. I cleaned up history, cookie, temporary files, reset security in IE options, still the same problem.

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Paul SDesktop Support Manager / Network AdministratorCommented:
can you post a screenshot of the 400 error and the exact behavior needed to reproduce it?
crcsupportAuthor Commented:
I'm sorry being late. Here it is.

crcsupportAuthor Commented:
I think I found the problem. The language setting of mailbox and internet explorer is not being matched. I had to either change language setting in internet explorer or in user's exchange mailbox.

To change through IE;
right click, then Encoding, make sure 'Auto-Select' is checked and UTF is selected.

To change  mailbox default language setting for OWA user;
crcsupportAuthor Commented:
as I found
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