We had a tip from a reader that the Windows Phone 7.8 update appears to have been causing issues with contact synching with Outlook.com, with the main issue appearing to be that contacts that are modified or added using the web interface of Outlook.com is not synching back down to the device. From searching around the net it seems to be a relatively prevalent issue.
To see if your device is affected:
If the contact does not appear you may also be afflicted.
If you have checked, vote in the poll below to help us see how widespread this issue is.
Thanks EvilEls for the tip.