We are sorry we could not get to you earlier today. We were trying to reproduce this but to no avail.
Thanks a lot for providing further details as they helped us locate the problem. Most likely, it is the CmsManager that is causing the problem. However, we will need some more time to find out what exactly the reason is.
We would recommend that you use the code below for time being. It didn't use to work before but now, with the latest RC1 update it is OK to use it.
this.PageTitle.Text = SiteMap.Providers["Allpages"].CurrentNode.Title;