Panel suddenly not working

[gv]

    Hi,

    Running the 4.4.1 ver since a while.

    Had to restart X today and panel vanished.

    In console, a xfce4-panel give me

    xfce4-panel: symbol lookup error: xfce4-panel: undefined symbol: 
xfce_itembar_set_allow_expand

    I've desinstalled (rpm) xfce4-panel and 45 plugins, reinstalled 
xfce4-panel, but same problem.

    Any guess would be appreciated.

Gérald