Outlook Errors on x64 XP Stations?

A new client to us in the middle of our network migration decided to order new x64 XP stations for their AutoCad people. Not having worked with x64 at all before it was a little different and you might encounter some strange problems in your SBS network.

One for us involved an Outlook 2003 issue. On just the x64 stations we could not connect to the Exchange Server without using "cached mode". We always received an error that the Exchange Server was unavailable. Also, when we did get in through "cached mode" the user would have to hit Send/Receive to get any mail and most of the time it just errored out with an "0x80040115 Connection to the Microsoft Exchange Server is unavailable". None of the other folders would synchronize and as you can imagine was most frustrating for the users.

Here's what we found after doing some good old troubleshooting:
In the Mail properties, Security Tab for Exchange Server we turned on the option to "Encrypt data between Microsoft Office Outlook and Microsoft Exchange Server".

Once we did this connection was made both offline and online and synchronizing of folders happened immediately. There must be a little problem with the x64 stations that require this. If anyone else has something to point to, please share but as for us we're happy now just to get the client going!