Textured mode problem

I’m adding a small veranda to my house, and designing it with Blender… mostly 2.54.

The veranda has a lot of glass (surprise, surprise) and when I render it comes out as expected, that is I can see inside where there is a tiny rock pool. When I use Textured mode however with glsl selected, although at first sight everything seems fine and I can see into the veranda, the rockpool has disappeared.

The plot thickens… If I lmb select the glass panes while still in Tectured mode, the rockpool reappears, if I select anything else, the rockpool disappears.

Gets even thicker… If I pan around -still in Textured mode- to look into the veranda through the glass roof , everything inside is visible.

The same thing happens if I load the model into 2.49.

I have checked the material properties of the side panes and the roof panes, and they are identical… I’m lost.

If anyone can suggest what’s going on, I’d be a lot less lost…