I will defend Larter. Her parts in Final Destination 2 and Resident Evil 3 were good acting. She looks competent with a gun in her hand. And she plays a split personality super power in Heros that spins your head. (Like Bishop, she looks good in dirt. LOL) While her actual physical attributes may look like the barbie cookie cutter, her acting ability is far better. She came across as the leader of the rag tag "normals" in RE3 very well and played off both Oded Fehr and Mila J. nicely. (Oh, heavens, is there any way to stick OF in this movie? Sorry, drool bucket time again. I sooooo missed him in the third Mummy movie. Not that Li isn't visually wonderful and kick ass on the action movie front, but I missed my tattooed desert dude. or TDD, as we referred to him on one of my other fan lists of the time. He'd make a good Alec, if you don't mind the slight accent that isn't Aussie/English

)
There is, mind you, a possibility that anyone could come across well with MJ and OF to work with.
And if we're going to get international here, there are a lot of talented asian/Indian actors to choose from for the "minor" parts, as well as French, German, Austrian and probably Arabic/African ... A well rounded cast would be nice. <disregard grumbles about last airbender and incredibly stupid casting decisions. If they could really act, it would help and if stupid directors would do their research it would help also!>
You're right about Portman, but I suspect she's too high profile for this movie. They're working with TV actors rather than movie actors.
I'm just kinda aghast that Paul and Virginia are the only parts that seem to have anyone attached, even peripherally, to them. UFO was, in many ways, an ensemble show, all of the parts being important on some level; not just the leads.
Oh, shoot, there I go again.