LTSP5 fluxbox desktop style anomoly

I'm running an LTSP5 system on Ubuntu heron using the "integrated"
ltsp. It's quite a bit different than what I call the "stand-alone"
version I used earlier with SuSE, but it's all running OK now. The
last problem I have is, when someone boots a client and logs in they
get a black desktop and no menus (we're using fluxbox.) The system bar
at the bottom is there and looks like the color and size we have set
up for the clients. but not the desktop color. The funny thing is that
if I log into the LTSP server as a valid LTSP domain user from my
machine using Xnest the desktop color is correct. It is harder to
differentiate where LTSP's environment stops and the server's starts;
much more so than the old LTSP3 and 4, and I'm having trouble knowing
where to look for solutions. Where is the file that controls the
desktop color for all logins?

thx,

tf