A few posts back, I showed you the basics of working with transparency in AutoCAD LT 2011. I hope you noticed the bit at the end about having to turn transparency on for plotting, since it’s off by default.
But you can also turn transparency on and off in your drawing as you work, similar to the way you can turn the display of lineweights on and off.
Transparency display is on by default, but with the icon indicated above you can turn it off.
Even if you think you’d never change this setting on purpose, it’s good to be aware of it, in case you get a drawing that isn’t behaving the way you expect it to.