Created attachment 3658 
X events for Super+g and Super+t

Since upgrading to Xfce 4.8 today (Xubuntu upgrade to 11.04), the hotkeys for applications (Einstellungen > Tastatur > Tastenkürzel für Anwendungen) have no effect when pressed. Hotkeys set for the window manager (Einstellungen > Fensterverwaltung > Tastatur), however, work.

For example:
Alt+F5, set for the window manager, maximizes/restores a window.
Super+d, set at the same place, shows the desktop.

Super+e, set for the keyboard (and set to execute Thunar), does nothing.
Super+t, set at the same place (set to open a Terminal), also does nothing.

The keys are recognized by the settings manager when I edit a hotkey.
The problem is not related to the Super key, as hotkeys set with other modifiers don't work also.

Output of xmodmap:
xmodmap:  up to 4 keys per modifier, (keycodes in parentheses):

shift       Shift_L (0x32),  Shift_R (0x3e)
lock        Caps_Lock (0x42)
control     Control_L (0x25),  Control_R (0x69)
mod1        Alt_L (0x40),  Meta_L (0xcd)
mod2        Num_Lock (0x4d)
mod3      
mod4        Super_L (0x85),  Super_R (0x86),  Super_L (0xce),  Hyper_L (0xcf)
mod5        ISO_Level3_Shift (0x5c),  Mode_switch (0xcb)

The output of xev (see attachment) shows that the keystrokes are recognized by X, and also that something recognizes the hotkey as such.
I ran "xev > xev.log" and pressed Super+g (not set to anything), then pressed Super+t (set to open a Terminal), then closed the program with Alt+F4. The log relevant to the keystrokes starts in line 202.

As far as I can see, instead of the KeyPressed(t) event, there is a lot of focus shifting. The screen also flickers as I press the 't' key.