SaveScreenShot not working

Hi,
Has anyone tried to use SaveScreenShot function with the last Web Studio 8.1 + SP1?
I save a trend in a popup window as a .gif file and then insert the picture in a .rtf file.
It worked with 8.0 and now it doesn't.
The function returns 0 (success) but no file is saved. Even $SaveScreenShot() does not save any picture.
Thanks for your help!