I was facing exactly same syptoms but with no OneNote involvement.
Here are couple of things that helped me get going:

I had installed a new version of Google desktop over last few days.
That also installs an addin to Outlook. Uninstalling that makes the
problem go away. Just disabling the add-ins from Outlook does not
help.

The other thing that worked was to start Outlook in safe mode:
Outlook /safe
Which, I guess, does not load the add-in.

So try launching outlook with /safe parameter, if that solves the
problem, an add-in is likely to be the problem.

-abhigyan

On Mar 13, 9:19 am, Tim <T...@discussions.microsoft.com> wrote:
> For almost a week, Outlook 2003 has been nearly unusable. I can receive and
> send e-mails, but with many limitations as noted below. I realize that itmay
> just be a coincidence that I recently installed an Office 2007 application,
> but previously I had not had any problems with my Office 2003 Professional
> installation. The other Office applications appear to be unaffected.
>
> Background:
> · Windows XP Professional Service Pack 2
> · Using Outlook 2003 Professional since Microsoft released it without problems
> o Synchronize Outlook 2003 with Palm Treo
> o Add-Ins: Google Desktop Search Outlook Addin,
> Chapura Settings
> & Exchange Extensions property pages (not sure why last one is installed,
> since I only use POP accounts)
> o COM Add-Ins: AttachmentOptions
> & ITunes Outlook Addin
> · About two weeks ago, installed OneNote 2007 Trial version
> · Last week, decided to purchase OneNote 2007 (a great application by the
> way): uninstalled trial, then installed full version
>
> Issues:
> 1. Context Menus: Right clicking on e-mail messages, appointments, tasks,
> etc. no longer display a context menu; functionality works within message
> itself (e.g. can forward a message after opening it by double clicking)
> 2. Appointments: Double clicking on an appointment in the calendar returns
> the error message: "Can't open this item". (Contacts, Tasks and Notes open
> fine.)
> 3. From/To/CC/BCC Buttons: Clicking any of these buttons returns theerror
> message: "The messaging interface has returned an unknown error. If the
> problem persists, restart Outlook."
> 4. Within Outlook, if I select Mail Setup, Data Files, then Settingsfor the
> Personal Folder where I store e-mail, the system returns the error message:
> "An unknown error occurred, error code:0x80040605." When I searched the
> discussion group, there were no postings with this error code.
>
> Steps Taken in Attempt to Correct Problems (not in order):
> · Ran "Detect and Repair" from within Outlook 2003 without and thenwith
> "Discard my customized settings and restore default settings" checked*
> · Ran "Microsoft Office Diagnostics" (installed with OneNote 2007; the
> previous version that came with Office 2003 was no longer available after
> installing OneNote 2007)
> · Uninstalled Outlook 2003 and reinstalled it
> · Uninstalled OneNote 2007 and reinstalled it
> · Ran ScanPST on file; corrected an error, but did not affect any issues
> · Created a new profile manually, scanned PST, renamed PST and associated it
> with new profile
> · Renamed MSMAPI32.DLL and let system replace based on another posting in
> forum
>
> * The strangest part of this problem, is that after I 'Detect and Repair"
> allowing Outlook to discard my settings, Outlook works correctly without any
> of the issues I mentioned above until I close it the first time. After I
> close it once, all of the issues return. Oddly enough, the system also
> insists on reinstalling the Redaction Add-On for Word each time it "Detects
> and Repairs", but nothing else.
>
> Thank you in advance for any assistance you can provide. I hope that my
> postings is not too long or too detailed, but I am desperate to get a
> solution for this problem.
>
> Tim