Confirmed. The account on SCALEO was created during setup as "Ulrich von Engelberg" and later renamed to "Ulrich". However, the "real" name of the account seems to remain unchanged, including the C:\Users subfolder.
When I try to establish RDP from SCALEO to VAIO, it says that it connects with user ID "Ulrich" but _actually_ uses "Ulrich von Engelberg" which doesn't exist on VAIO. After explicitly entering "Ulrich", it works. The other way, connecting from VAIO to SCALEO I have to enter "Ulrich von Engelberg" as user, otherwise it will fail.
After renaming the user account back, creating a new one named "Ulrich" and deleting the old one, everything works fine now.
Summary: When renaming a user account, there is a "Display name" (the renamed one) and a "Real name" (the original unrenamed one). When connecting via Remote Desktop Connection from such a renamed account, it shows the display name but uses the real name. When connecting to a renamed account, the real name instead of the display name has to be used.
To avoid such problems, don't use the "rename user account" feature. Better create a new account with the changed name, copy the settings and delete the old one.
This is perhaps not even new Windows 7 behaviour, but I think it is unexpected and very confusing.