After the first attack, you no longer have the invisible condition, so the rest of the attacks are as normal.
Edit: Corrected myself. :)
First attack only unlees the invs is greater invs. Casue after you attack you are no longer invs.
With the invisabilty spell,
When you attack you appear,
But is only your first attack sneak attack or all of them for that round?
Since wouldn't they be flat footed for you tell the start of there turn?
You become visible after the first attack, so only the first attack is viable for Sneak Attack (unless there is some other factor, such as flanking & such).
Important distinction to make: Denied dex bonus =/= flat-footed. Flat-footed means they have not yet acted in combat, which typically only occurs during the first round of combat. When someone is invisible, you are not flat-footed to them (because "flat-footed" doesn't specify targets- you're either flat-footed, or you're not, regardless of who is attacking you), you are denied your dex bonus (which is what allows a rogue to sneak attack you). If the target was flat-footed (such as during the first round of combat), then yes, they would remain flat-footed until their next turn, but if you're invisible, they are only denied their dex bonus until you become visible- that is, after your first attack.
With the invisabilty spell,
When you attack you appear,
But is only your first attack sneak attack or all of them for that round?
Since wouldn't they be flat footed for you tell the start of there turn?
If your in combat, you become aware of them when your kidneys develop puncture wounds. From there, you are aware of them and can take them into account on your normal 'defense' that goes into your AC.
HOWEVER, if the scen your talking about is your OUT of combat, we drop into the surprise round rules.
If you don't detect them, you don't get to act and are flat footed in the surprise round (No full round actions from memory). Whether they are invis or just sneaky doesn't matter here.
In the first 'real' round though... If you haven't acted, I'd assume your still flat footed. In theory that rogue could shank you in the surprise round, then (if he rolls well enough on init), continue to apply sneak attack to you in the first 'full' round of combat while your still getting your bearings and are processing the fact that your under attack.
Try not to let that happen to you. It hurts a lot.