Error Samgung Galaxy

Hi, I´m starting to learn Unity and Android, and I´ve got this problem:
I´ve got a Samgung Galaxy s Duos, I´ve created a scene with Standard Asset Mobile, then I´ve done a “build” and I´ve installed it in the mobile and when I open the game, there is a trail when the character moves. I don´t know why this happens, I´ve built it in the different versions of Android (I´ve got 4.0.4 in my phone) and it always happens the same.

Besides, I´ve got another problem with Unity Remote, I can´t make it work, I´ve followed the instructions from Unity Remote for Android – Through the Eyes of Keaven, but the image remains still in the remote “ Connect this device with USB cable…”
I would thank any help for any of these problems.

Please check if your camera is clearing the screen.