That dusty looking film on top of the pavers is most likely polymeric haze. When they sand the joints, they spread a polymeric sand out on the pavers and sweep it into the joints. Then they run a vibratory tamp over the top of the pavers to help settle the sand into the joints. All that sweeping and vibrating leaves a layer of dust on top of the pavers. The polymers in the sand sets up when it is exposed to water so water is sprayed on top of the pavers to set up the sand down in the joints. Unfortunately the poly dust sets up on top of the pavers leaving that dusty looking film.
The poly haze is easiest to remove with hot water.... I can't over emphasize the use of hot water on removing poly haze. As long as the polymeric sand has had time to fully set up, it shouldn't come out with a surface cleaner if you do like others have said and use at least 25 degree nozzles. One thing to remember about cleaning pavers. Don't go so fast that you leave swirl marks and make sure you clean every square inch evenly. When the pavers are wet it may be hard to tell if you have left any marks or not or missed any areas unless you look very close. Even when they dry you may not see any imperfections in your cleaning. However, if a sealer is applied to the pavers later, these swirl marks or missed spots will stand out like they have a red flag pointing at them.
Another thing to note about paver cleaning that I am running into these days. Just a few years ago, paver manufacturers made pavers like crazy and stock piled on their yards knowing they would be sold at some point. It was possible the pavers could sit on the yard for a year or more curing out. In today's economy, paver manufacturers are more or less making pavers to order and shipping them straight out to the job-site.
These new pavers don't not have the time to cure out like they used to and once they are put in place the efflorescence comes to the surface.
Dealing with efflorescence could be a whole new topic, but what you want to do is make the owner aware of it and that it would probably happen normally with rain anyway and that your cleaning may make it happen sooner. If after you clean the pavers and a few days later they start turning white primarily around the edges, you don't want the owner to freak out and say you ruined his pavers.
You might also tell the owner not to have them sealed for several months until it is sure the efflorescence will not be a problem.
Call me if you like if you have any more questions.