Dynamic texture problem

I’ve been working on a simple OpenGL game under Linux (TNT2) for about three months now, when I get time. I use a transparent texture-mapped cone for thrust on my ships. The texture map is algorithmically generated, and replaced once per frame when it is on with glTexSubImage. Unfortunately, this texture SOMETIMES appears garbled. I will see if inserting HTML works here, to show you the pictures. If not I hope the tag will at least appear as text. Here is the way it looks when garbled:

And here is how it should look:

Does anyone know why this might happen? I wanted to ask here before I rip the code up, since I’ve tried a lot of things with no definitive answer. It is affected by the dimensions I make the texture map, whether the ship’s shield is on or not (that’s the variable in the pictures), which ship is drawn first, etc. I have tried pushing and popping all lighting attributes, but that didn’t seem to help. Any ideas would be greatly appreciated


might be something else, but are you real sure that your texture map is ALWAYS correctly created?