I believe this is happening because of the way the TribesNext patch is loaded. When TribesNext is loaded, it is loaded from a .dll that has been injected into Tribes2.exe which is what a lot of viruses do to .exe files. This is a false positive. (But, still be careful!)
EDIT: Found Thyth's post about it:
The TribesNext patcher adds a new executable section (containing code to load the TribesNext DLL) and jumps to it when T2 starts, which is vaguely similar to how viruses used to infect executables.
LouCypher implemented a different loader that replaces the Immersion Force Feedback DLL, and initiates TribesNext that way. It's something I'm planning on implementing in a future version of the TribesNext patch. You can try using LouCypher's replacement IFC22.DLL with the original (unpatched) Tribes 2 executable. Download from: http://rdb.internectual.net/t2
By the way, if you use the IFC22.DLL method, you need to enable the "Force Feedback" option inside Settings -> Game for it to actually work.