To clear that up for my world here are the additional rules:
1. If an enemy perceives you, even if you are invisible to some sense, you do not gain CA unless you have it some other way. Invisibility is treated as total concealment.
2. If you speak you lose hidden status.
3. If you speak you are +3 on stealth DC rolls until SoNT. +6 if you yell.
4. If you attack you lose hidden status.
5. If you attack you are +5 on stealth DC rolls until SoNT. +8 if the attack is loud, +11 if it's very loud
6. Speaking and loud attack modifiers take only the worst one.
7. If a move action includes athletics or acrobatics then the stealth DC is +2.
8. Total concealment or superior cover is a +5 DC to perception checks (not +10)
9. Partial concealment or partial cover is a +2 DC to perception checks (as normal)
10. Anything above a half speed move is +3 DC to stealth, regardless of abilities.
11. If you are in the open and do not generate your own concealment, you cannot become hidden, even if your power says you can.
12. Any attack from hidden forces a free perception check on the target. That perception check must beat the stealth of the attacker to prevent the CA. This is a check BEFORE the minuses from the hidden person attacking which only take effect after the attack. Remember that there is only 1 perception check per round.