First, let me say that I have tried Symantec tech support repeatedly on this question. I am a software developer and a software product of ours has some type of conflict with a couple of specific versions of Norton Antivirus. Specifically, we are experiencing problems with NAV 2000 Version 6.10.20 and NAV 2001 7.00.51F. Earlier versions prior to 6.10.20 and versions later than 7.00.51F do not appear to have the problem with our application. Disabling NAV makes the problem go away. We get either a OE exception with blue screen on windows virtual driver vxd ifsmgr(04) or we get invalid page exception on our program. We get many reports from our customers and have also recreated the problem in-house. The application is primarily a DOS console application running in Win9x written in Visual C. The problem occurs when our applicaiotin issues a system call to run a dir DOS command. The computer hangs and typically cannot recover. Searching for an answer, found where Python (open source Python programming language) also had a similiar problem with Ver 6.10.20. Any help would be appreciated.