8GB screen problem - brightness

I recently received an 8GB sansa clip.  The screen randomly switches from very bright to being so dim you can barely read it.  I’ve tried changing the brightness settings but this has no effect on the screen at all.  Yesterday it remained black the entire time (its very frustrating trying to guess at the menu options in the dark!)  Please help - I’d greatly appreciate some suggestions! Thanks!

Return and exchange–it’s defective.