Hopefully the version we're using isn't too old to get some positive feedback
What is happening is this:
We've (150+ users) recently upgraded from RHEL 3 + KDE 3.1.3-6.10 and are running into some quirks with 5.2 + 3.5.4-16. We've worked through most of them, but there are still a few lingering.

On my machine, the xinerama screen is set to 2 so the taskbar only spans screen 2 and not both screens. It seems that kwin(?) thinks the taskbar is spanning both screens because on screen 1 window titlebars can't be moved onto the space where the taskbar would be if it spanned both screens.

This behavior is exhibited when the taskbar is either on the top or bottom of the screen.

Other users are experiencing this issue.

Another oddity is on the previous version we were using, the titlebar of a window could be dragged off the screen. It's restricted to the edge on this version. Being able to drag off the screen is useful to me because I use remote desktop to connect to an XP box. Without that capability, I can't get to the XP taskbar in the remote desktop session. So far, I'm the only one experiencing this.

Anyone run into problems like this? Are there known issues around them?

Thanks,
- Doug

Xinerama is likely causing KWin to think that the Panel spans both windows unfortunately.
Don't know about the multi screen drag off protection however ( except that it isn't implemented under KDE 4 )