You are running Windows Vista Or 7 Right?
well, Vista and Windows 7 has a Theme (style),
Remember Windows XP, there was Windows Classic , Windows XP Olive, Windows XP Silver, Windows Xp blue?
Windows Vista and 7 has a Skin (theme, style) Called Aero, But it's alot more powerful then your traditional skins .
When the Aero theme is enabled it masks the DevComponents, In order to correct this, You have to disable the Aero theme, Now you can do this in you Control Panels or Themes manager , but that will only work locally, anyone on a Vista or 7 Machine with Aero Enabled will have the same problem when viewing (using) your application.
So I suggested you use one of the codes above to disable Aero , or offer the option of disabling the aero theme inside of your application.