I’ve been running Windows Vista Ultimate 64 bit for 3 months now and recently started having problems syncing my Motorola Q.
When I would try and launch Windows Mobile Device Center 6.1 nothing would happen and this error message would show in the event logs:

Failed to start the Windows Mobile-based device connectivity service due to EnableRAPIMgr(0×80070005) failure (see data for failure code).

When searching the internet for a solution I found the following solution:
The solution:
Run in a cmd prompt:
net localgroup Administrators /add Local Service

Here is a link to the Microsoft Forums Discussion on this topic http://forums.microsoft.com/windowsmobile/ShowPost.aspx?postid=2989559&isthread=false&siteid=65&authhash=b791a1d36fb36c638c9885b250097b4589f542e3&ticks=633408613414984248