hmm, odd.
My next guess would be that java2d acceleration is somehow causing a clash with lwjgl, this is one of the common problems with AWTGLCanvas (which Display.setParent() doesn't suffer).
any way you can get the user to run lwjgl with the following java vm arguments?
-Dsun.java2d.noddraw=true -Dsun.awt.noerasebackground=true -Dsun.java2d.d3d=false -Dsun.java2d.opengl=false -Dsun.java2d.pmoffscreen=false