One more thing to try, just to weed out variables:
1) Edit /usr/share/themes/Ambiance/gtk-2.0/gtkrc
2) Find the following line: bg_pixmap[NORMAL] = "panel_bg.png" and change it to: # bg_pixmap[NORMAL] = "panel_bg.png"
This will disable the background image on the panel. Post back here with results.
One more thing to try, just to weed out variables:
1) Edit /usr/share/ themes/ Ambiance/ gtk-2.0/ gtkrc
2) Find the following line:
bg_pixmap[NORMAL] = "panel_bg.png"
and change it to:
# bg_pixmap[NORMAL] = "panel_bg.png"
This will disable the background image on the panel. Post back here with results.