Faces disappear in texture mode

EDIT: Accidentally posted in the wrong forum section, could a moderator please move this to the modeling section?

Hi, I’m having a problem with a model I’m trying to make. When in solid mode, everything appears normal:

i.imgur. com/05TVe.png

But when I switch to texture mode, some of the faces disappear:

imgur. com/ugRLs.png

I tried using “f” to add faces but a message appears saying they already exist. I can’t apply textures to the invisible faces. Can anyone help? Thanks

Try recalculating the direction of the face normals (Ctrl+N)
Always best before you do this to remove any double vertices, select all vertices and W /Remove Doubles

Thanks, that worked perfectly!