Version:            (using KDE 4.4.0)
OS:                Linux
Installed from:    Ubuntu Packages

 I'm running kde 4.4.0 on kubuntu 9.10 on an Asus EeePC 1000h, freshly installed. I'm currently using the netscape form factor (set in System Settings->Desktop->Workspaces->Netbook form factor), and I wanted to experiment with adding more activities (or pages as they're called in the netbook form factor), and of different types than the standard SAL or Newspaper activities. 
 So I go to Page One, click the cashew, click "Add Page", a new activity or page appears, click "Configure page", go to "Activity" in the config window, change the type from "Newspaper activity" to "Desktop", klick OK. Now the cashew disappears, but a cashew tab appears on the right side of the screen. Now when I want to add widgets to this desktop activity, I click the cashew side tab, click "Add Widgets", and then the "widget panel" appears briefly from the top, and disappears immediately. The widget panel remains transparent when it appears, no widgets are drawn on it. The same happens when I access "Add widget" by right clicking the desktop, or by pressing Alt+D,A. For an image of this, see the attachment (there's actually three pages in there, I added a Newspaper page first).