Hi Richard,
I just took a quick look at the code in ~/Services/UserDropDown.aspx.cs and much to my horror I see a hard coded siteID = 1
That certainly explains the cause of your symptom, much to my embarrasment
The fix is to add:
SiteSettings siteSettings = SiteSettings.GetCurrent();
and then pass in siteSettings.SiteID
I will fix that tonight after work and commit to svn.
Cheers,
Joe