changing background wallpaper remotely hangs winvnc?

[ruamdro]

Hello

i have "bginfo" (systinternal) run every time i log on for the first time.
A window pops up where i could say which parameters should be displayed as wallpaper.
Too there i a point to enable the background wallpaper.
If i do that remotely, the winvnc immediately hangs.
The mouse freezes if dealt with by server. There is no refresh anymore On the local screen of the server there the mouse can be moved etc..
I still can "connect" to the server. Say client is waiting for protocol nego, but nothing happens.
I can do net stop ultrasrv, net start ultrasrv, but no success:
No remote access.
If i kill in taskmanager the winvnc process and restart the vnc server, all is well again.
Bug or feature?

i have tested that without mirror driver and with.
It's cmpletely reproducibe. but i don't really think that's a feature.

Is a a bug?
Why?

(Workarround: don't finger at the wallpaper remotely)