Question : ActiveSync http error 500/400--All mobile devices--

Here's a great one for everyone.
I have been getting the dreaded http error 400, event ID 3005 error on a Windows SBS 2003 SP2 server.
I have done some extensive testing using Win Mobile 6 emulator and an iPhone.
Exact errors:
Unexpected Exchange mailbox Server error: Server:xxx.internaldomain.local User: [email protected]  HTTP status code: [400]. Verify that the Exchange mailbox Server is working correctly.
Exact same error as well with http status code of 500.

What I have done:
Reset ALL associated virtual directories and permissions.
http://www.experts-exchange.com/Networking/Email_Groupware/Exchange_Server/Q_21752093.html
http://support.microsoft.com/default.aspx?kbid=883380
I have also gone through:
http://forums.techarena.in/small-business-server/656570.htm
I turned off all ability for OWA/syncing for all users except one so don't generate any giant logs during fixing this.
I also deleted out the Exchange Virtual server Micosoft-Server-Activesync VDIR from ESM, and recreated it.

It seems to take about 15-30 minutes before the 400 error begins to log, and the devices stop working correctly.  If I restart IIS, everything is golden again.  I have tried about everything I can think of and google to fix the problem.

Other items I am thinking of:
Database is 19GB, which is a bit large for SBS standard..so I will have to trim that down, but that shouldn't affect syncing.
Plenty of hard drive space.
There is another website hosted on this server outside of "Default Web Site" (simple html company website) designated via host headers.
This machine has 3 nic's, one is failed and disabled (onboard), one is primary network NIC, and a third for an iSCSI san.  So, on the Default website, I do have an IP address designated to it (I know this is a no-no, but it doesn't change my results).

I think I may just be stuck on a specific line of thinking, so I am open to all suggestions.
Thanks in advance!
DD

Answer : ActiveSync http error 500/400--All mobile devices--

Please have a good read through my Exchange 2003 / Activesync article, which should give you all the details you need to get you working:

http://www.experts-exchange.com/articles/Software/Server_Software/Email_Servers/Exchange/Exchange-2003-Activesync-Connection-Problems-FAQ.html