As far as I can tell, both <Tab> and <Enter> keys, by default, do the same - navigate to the next (navigable) item. If it doesn't work for you, I suppose that "you" (or someone who did the setup) modified that. KEY-NEXT-ITEM trigger isn't to be blamed as it would capture both <Tab> and <Enter>, so it might be the key mapping configuration file - search for .RES file and check what's in there. I *think* that <Enter> is mapped as <Return> (but I'm not sure).
Do some research by yourself; I found this blog entry - perhaps you'll find it useful.