Contributed by B@rt.
First of all, make sure that the dimensions of your textures are multiples of 64 pixels - this is a hardware requirement of most OpenGL game videocards.
Next, make sure you have actually applied the UV textures correctly. Maybe these tutorials can be of help:
https://members.yourlink.net/gruff/pink/
https://www.blender.nl/showitem.php?id=20
Contributed by Nathan Vegdahl.
There are several possible reasons. The first one that you should check is what you have the OpenGL rendering mode set to. Make sure that it is set to texture mode (CTRL-Z ? Whoever publishes this for me, please make sure that that is the correct hot-key).
The second thing you should check is how you are mapping the texture onto the object. Regular Blender materials do not work with interactive game part of Blender. To map a texture onto an object that will be used in a GameBlender game, you must use the UV editor.
The third and last thing to check is to make certain that the texture dimensions are multiples of 16, because OpenGL does not support textures with dimensions that are not a multiple of 16.