I tried:
- disabling the addin in Outlook: no effect,
- removing the MobileMe Control Panel via Control Panel>Add or Remove Programs (no-go there, as there is no Uninstall option),
- flushing iTunes, Apple Sofware Update, Apple Mobile Devices Support, Bonjour and Apple Applications Support using Revo Uninstaller on its most aggressive setting and then re-installing iTunes: no effect.
In the end, I simply renamed C:\Program Files\Common Files\Apple\Mobile Device Support\OutMMe32.dll to OutMMe32.dll.rjs
Seems to be a safe workaround; Outlook is back to its original behviour and iTunes is fine (or as much as it ever was, anyway).