it's known that there is massive parallism in the brain, and it is also known that we can only think sequentially, one thing at a time, so the question is, 'How do you resolve this seeming contradiction'?

How's about the idea that the outputs from the parallel activities will have different significance and different times to 'realise'. Then it is possible that an non-concious prioritisation centre might filter those parallel outputs by those two parameters so that we are only aware of 'one thing at a time'. The rest are queued.

I think Rhymer might have something there. Maybe the parallel stuff is unconscious and the conscious stuff is serial. That might explain a role for consciousness in organizing (serializing) mentation. Therefore, a philosopher's zombie (who behaves like us but has no qualia) would no longer be logically conceivable.

what would be the purpose of serialization? To benefit motor actions? Where would this queuing take place in the brain? It's an interesting idea.

Algorithms (action plans) are frequently sequences of steps. First catch the rabit, then gut it, skin it, and then put it over the fire.

Or maybe it's just situational awareness. A cat watching for prey is aware of "now" as one thing, one situation, in a sequence of moments.

Or maybe it has to do with time and memory. Without memory there is no sense of time (no earlier remembered stuff). Sequences of times make for convenient memory storage: first I drew the bow, then I let the arrow fly, then the arrow hit the rabit.

Queuing would seem to be a necessary thing in a system which has to evaluate a cost function ( what is the most "benefical" action ) that I can take, its probably a priority queue

I don't think any memory is stored non sequencally. If someone asked to you describe your house you would take a "virtual" tour of it and describe it one part at a time as if you were exploring it, you can't communicate it's "wholeness" at one time, something prevents that in our brains. Sequences allow allow our memories to be stored so that when the sequences are preserved we have implict time ordering with time invariance all in one package, so that we can associate events which occur across "large" gaps in time even.