Im having trouble in Blender?

Well, I am becoming more avid in the 3d modeling program Blender. Myself and a few friends are trying to make a game. And the other day i modeled a "Level" Just a little thing. Nothing major. And i textured a bunch of stuff. I was really proud of my work. (I modeled it on my friends computer btw.) Then something happened and none of the textures showed up. All of the objects are still textured but they dont show up. Can anyone help? And also. Whenever i am in GLSL mode and texture something the textures dont show up. Does anyone know why and how i can fix it? Please help.