Some Outlook items no longer syncing

My environment: I'm using Vista Business (32-bit)/Windows Mobile Device
Center (WMDC) and Outlook 2007 with WM6.1 on a Sprint HTC Mogul 6800 PDA.
Synopsis of problem: I noticed recently that some items including Outlook
Tasks and Appointments had ceased syncing correctly, although OneNote,
Folders and Favorites appear to be syncing ok. On further investigation on
the PDA I found that I'd now (inadvertently) got two differently named
set-ups for syncing, one called Windows PC and one called Windows PC2, even
though I only ever sync with one laptop. With Windows PC2, which appeared to
now be the default, Contacts, Tasks and Appointments etc were all greyed out,
presumably why these items had not been updating lately.
Actions tried so far: I tried to revert to the 'Windows PC' profile for
syncing but kept getting error messages and was unable to select that set of
sync items. Next, I tried to rename the laptop in WMDC to create a new,
third sync set up, but that didn't work, either. In Control Panel I
'repaired' WMDC - this made no difference. I uninstalled WMDC, downloaded
the latest version and installed it - no difference. After most failed
attempts to sync, I have rebooted the laptop and done a soft reset on the PDA
but the problem persists. I deleted the partnership with the Mogul and
recreated it. On first connection after this, WMDC says 'Outlook has not
been installed' under each of the greyed out options: Contacts,
Appointments, Tasks. I had a similar problem once before and was advised to
repair WMDC in Control Panel but this time that has had no effect. I've
searched the newsgroups and various forums for similar symptoms and have
tried most suggestions (as described above) to no avail. I'm not aware of
any changes or problems occurring in Outlook on the laptop which would have
caused these symptoms. All my Outlook data is in my Outlook.pst file.
Next steps: I'd like to try and avoid doing a hard reset of the PDA. Is
there anything else I can try before I resort to that? What could have led
to the two sync profiles (i.e. Windows PC and Windows PC2) being created and
what should I watch for in future to avoid this happening again?