Everyone can still see me. I cast invisibility and try to sneak past two saber cats, and they maul me. Potions do the same. Am I missing something?

Just because your invisible doesn't mean they can't hear you. Cast muffle and then invisibility and you should be good.

Enemies can still hear you. Do you have on loud armor? How high is your sneak skill?

Yes, you need to be sneaking and muffled.

Invisibility removes sight, there is still sound, and if you are not sneaking animals can detect you- humans wont if you are just invisible and muffled, animals will.

Never used muffle once and have been caught sneaking, even when not invisible.

No they won't, I'd you're silent and invisible with a decent sneak skill, nothing will detect you unless you bump into them.

Yes... they will. Read my post carefully. I am talking about muffle and invisible --without-- sneaking. Humans will "detect" you, but cant get a lock on you and attack effectively, but animals will detect you with both muffle and invis unless you sneak.

That is why i said he needs to be in sneak mode as he is specifically mentioning an animal detection.

The only times I've ever had a problem with Invisibility is when I've been heard (moving too quickly usually is my downfall in the beginning) or when I try to go invisible in the middle of a fight.

In the latter case, it only works if I get out of the area and break what would be the enemy's line of sight, then I have to find a quiet spot and wait for [Hidden] status again.