Open the Uifile in your logon folder and change line 14 at the top of the file from this:
background: rcbmp(100,0,#0,0,0,1,0);//rcbmp(100,6,#FF00FF,0,0,1,0);
To this:
background: rcbmp(100,0,#FF00FF,0,0,1,0);//rcbmp(100,6,#FF00FF,0,0,1,0);
That usually will solve the problem. Don't open the logon in the Logon Studio Editor after you do that, or it will change back...you have to do it as the very last thing.
Not all wallpapers have that problem, but when they do, that fix should work.
