not the same thing but i saw a grenade go off next to someone then he ran off. don't know the server name bit its got the plane to keep ppl off a roof and going underground.

As I made some nearly invisible skins ('predator'-like ones, available [url=http://www.alliedassault.com/pafiledb/pafiledb.php?action=file&id=515:7a103]here[/url:7a103]), it is possible to make totally invisible ones. But you can not 'see' it (well, hope you understand what I'm trying to say) unless you AND the server have downloaded them. Maybe some funny guys have made a cool mod/map/skin you dowloaded, but they included the invisible skins in the pack... Just explore your uniform skins in the multiplayer options to see if there is an hiding one.

i bet its just a glitch in the game.

sounds more like another form of cheat to me :x

Its a video glitch. Do what the others said and it'll fix it.

Problem is, how do you KNOW if someone is invisible if you can't see them? :)

Well, I've seen that when the glitch happens, you'll find a model frozen on a spawn point somewhere. So if you see a frozen model in a map, you have someone wandering around invisible. They won't know though.