Comment 5 for bug 603907

Ah, I see what you are talking about, these "lines" are called panels. Normally when people talk about lines on the screen, they are seeing visual artifacts due to poor video rendering.

You can change the user preferences to not use desktop effects (comipz). Go to System->Preferences->Appearance. Under the Visual Effects tab, select None, then Close. Re-add the panels through whatever means you have been doing so that you have the top and bottom panel. Now reboot the system - do the panels remain or are they gone again?