I will be glad to help, however, in order to find a solution I'd need the complete information regarding the problem.
1 - Please include the title, version, and platform you are using. On the PC you will find this info in the main menu =>Help =>About… On the Mac this info is on the title menu =>About…
See => http://forums.turbofloorplan.com/index.php/topic,3231.msg15856.html#new
If possible, add information regarding OS, computer capability, video card, etc. This issue can be related with a hardware problem.
2 - Not sure what do you mean by "transparent walls". Can you post a screenshot of the problem?
3 - Does this problem happens with all the files or just with this one? Can you inform the size of the current file (in Mb)?