All questions and problems regarding LXDE components including LXSession, LXAppearance, GPicView, Leafpad, LXTerminal, Xarchiver, LXNM to be discussed here.
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The OP was using Debian Sid (unstable) and the post was 1 1/2 years old. Do you have a problem related to it? The post is probably overcome by events being as old as it is.
Well, there's not much for the rest of us to go on with. Perhaps you could describe your system in some detail? OS, themes, etc.
Also, not that it may be significant, but OP ran lxappearance from root. I wonder why.
I've tested with a full load of GTK engines installed and have also removed all Themes. Same issue.
If I remove the obconf component of lxappearance, then lxappearance will run.
Were there some changes made to this applet recently?
I run Debian Testing (Jessie) and Sparky Linux (Debian Testing based) with lxappearance 5.2 and they all execute correctly, both from lxterminal and Customize Look & Feel. Similarly for a Crunchbang (Debian Testing based) install with lxappearance 5.1. Obconf 2.0.4 is installed in all 3. I do not think your problem is with the lxde desktop.