grassy knoll

I finished the, the third man missioin i got to act 2 mission 25
where i get the mod and the way points to look for the marauders
and then blow up the station and the cruiser. i believe that's it.
But I still have in my objectives that say act 2 mission 10 grassy knoll and act 2 mission 8, corporate holdings. Why won't they get off of that. This is really getting on my nerves. If I didn't complete them then how in the hell am I at act 2 mission 25.
After I finished that I got no more mission to go on, How come ?
what do I have to do to finish this game. Please HELP me I'm stuck.