A simple mistake with an equally simple fix.
--- desktop-menu-plugin.c 2007-11-17 14:31:41.000000000 -0500
+++ desktop-menu-plugin_new.c 2009-01-20 10:32:33.000000000 -0500
@@ -154,8 +154,8 @@
gint width, height, size, pix_w = 0, pix_h = 0;
GtkOrientation orientation = xfce_panel_plugin_get_orientation(plugin);
- size = wsize - MAX(GTK_WIDGET(dmp->button)->style->xthickness,
- GTK_WIDGET(dmp->button)->style->ythickness) - 1;
+ size = wsize - 2 * MAX(GTK_WIDGET(dmp->button)->style->xthickness,
+ GTK_WIDGET(dmp->button)->style->ythickness) - 2;
DBG("wsize: %d, size: %d", wsize, size);