I also cannot reproduce this problem in my x64 machine. I have strong feeling that it is related to specific machine configuration or specific dataset. So if we can get below information, it would be helpful.
1. Inventor version (2008 or 2009)?
2. Can it be reproduced when saving .ipt or .iam in user's machine?
3. Can it be reproduced in other machine?
Raymond Xu
Autodesk Inventor Developer
Raymond Xu
Software Architect
Autodesk, Inc.