CITRIX isn't a Window Manager.
It looks like Gnome2 is the default WM for RHEL 5.8 but I can't find anything that explicitly states that.
Gnome2/Mate (Metacity/Marco):
System -> Preferences -> Keyboard shortcuts
Set the shortcut for Move between windows, using a popup window (default is Alt+Tab). It's possible you are using Compiz or another WM though, so figure that out.

However, noticed you mentioned konsole, the official KDE terminal emulator. This suggests you may be using KDE. To switch tabs in konsole the default is Shift+RightArrow or change it Settings -> Configure shortcuts -> Next Tab.

To switch windows in KDE Alt+Tab or change it System Settings -> Window Behavior -> Task Switcher -> All windows
