Just blithering on about the "virus" is not going to get us anywhere. Let's stay on topic about this and try and get what we know together.

Description: The virus changes your local F9 players list so that all the names are bad words. It does not affect anyone else in the server. It may warp you around and turn your screen black, but that could be something else.

Who has it: UmbaMan, Tazz, and Goldy. BunnyElmer may have it.

Other information: It does not disappear when you reinstall JJ2, but may have a time limit as to how long it will continue working.

My hypothesis: This "virus" is an external program that does memory hacking to do this stuff. Most likely it was made in Visual Basic. It has probably been disguised as another program, such as a trainer. With only three or four people having it, it is likely that it is not spread through JJ2.

What I want to know: Do the people who have this virus use or have used any pre-made trainer at any time? It doesn't matter if it is multiplayer or single player. If so, what program(s) have you used? What do they do? Who gave them to you?
When this virus is occuring, press Ctrl+Alt+Delete, and see if there are any suspicious things running.