As explained too many times already, some antivirus are wrong (Norton and McAfee being the biggest offenders), and report this as false positive. The solution it's always the same:
- Turn off the antivirus before downloading and installing
- Configure the antivirus to exclude the following files from scanning BEFORE launching FSX:
YourFSXFolder\bglmanx.dll
YourFSXFolder\fsdreamteam\couatl.exe
YourFSXFolder it's usually C:\Program Files\Microsoft Games\Microsoft Flight Simulator X, if you installed it in the default folder.
Better solution is switch to a more realiable antivirus program, like the free Microsoft Security Essentials, which is very light on system resources, it doesn't mistakenly identify our stuff as threats, it's better integrated with the system, and it's always updated without being tied to a subscription.