stand up= action?

[Da Crusha]

is standing up considered an action? I would think it was a move action since it takes 3 movement to do it.

will standing up prevent you from attempting a block?

can someone who is knocked down, stand up and foul someone who is knocked down and next to them?

[Greyhound]

stand up is not an Action.
stand up can be used as part of a move action (free of MV with Jump up or for 3 MV without the skill)
stand up can be used as part of a Block action (with the jump up skill)
stand up can be used as part of a passing action and will be eating some of your movement before the pass (free of MV with Jump up or for 3 MV without the skill)
stand up can be used as part of a foul action and will be eating some of your movement before the foul (free of MV with Jump up or for 3 MV without the skill)

stand up cannot be used as part of a throw a bomb action as indicated in the rule.

Did I forget an action?... oh yes, Blitz,
stand up can be used as part of a Blitz action (free of MV with Jump up or for 3 MV without the skill).

[nazgob]

Equally important, standing up may not be part of a block action if you do not have the jump up skill. so no standing up and blocking in most circumstances.

[Greyhound]

Equally important, standing up may not be part of a block action if you do not have the jump up skill. so no standing up and blocking in most circumstances.

Absolutely. Standing up = moving (not it differs from a move action),

[burgun824]

To summarize...standing up is like taking a move action unless you have "jump up."

[Da Crusha]

got it! thanks a lot guys.

[duckwing]

To summarize...standing up is like taking a move action unless you have "jump up."

Or rather, standing up is part of a move action (if that is all the player does)

[burgun824]

Correct.

[Greyhound]

Also important to clarify all the "Can I use wrestle then standup again" usual questions:
from the rules:

you can only stand up at the beginning of an Action

[duckwing]

Wrestle would have been awesome if you could stand up and continue moving afterwards.