This is really weird. I haven't been using Terragen much recently, but in the time that I used it (the unregistered version) I never encountered this problem. Would you like to send the file to me, see if it renders out OK? IM me for e-mail address. I haven't updated to the latest Terragen, so I'll try on my current setup, then update, see if it's a bug. Wonder if files are backward-compatible.....which version are you using?