How's the bird population in your neighborhood? You won't believe me, but small birds often look for moisture and bugs by pecking at nice lush green leaves, especially bean leaves. Here's an excellent video explanation by a friend in Fremont:
http://www.youtube.com/watch?v=r_14MDmViWo

The little lacey trail is fungus being traipsed across your leaves by the marching feet of whatever critter is visiting your vines. The dearth of sunshine and the straw have brought new spores to your area! The straw is actually more to blame than the sun. It ferments, molds, mildews as it breaks down and your little visitors run across it and carry it up to your plants.

Couple of things to do: spray well with an organic fungicide (they DO exist). Make sure you spray the straw too!! Cut off anything that turns yellow or brown and remove it from the area. After spraying, rake out that straw. Rake it AFTER you spray so that the spores that get kicked up wont affect anything else. Normally, if this were a recurring fungus that you've had before, I would say go ahead and add it to the existing compost pile since you're already (technically) taking care of the fungus. Unless are getting ready to add raw manure to the pile, which will raise the heat high enough to kill it......I wouldn't. Set it aside in the place you are planning to flip or start a new compost pile, sprinkle liberally with lime, and then ash, then manure, and then start piling on your organics. This way you start your new pile , but in such a way that it gets cooked and doesn't have any way to spread to the rest of your garden.
Note: If your beans have it, your squash, cukes, melons will start showing symptoms too. Spray them at the same time and save yourself the heartache!

Here is a link that might be useful: Planet Natural

Where do you get a fungus problem from twc's description? I don't get that at all. Educate me.

It sounds like skeletonizing caused by an insect...perhaps bean beetles, as a matter of fact. Several insects and/or their larvae skeletonize (lacify) foliage.

Mexican Bean Beetles, cousins of Lady Beetles, will make lace of the leaves of bean plants. It is highly unlikely that the sow bugs are the ones doing that.
Control starts by planting early crops so they are producing before the adult beetles arrive, floating row covers, attracting predators of these buggers such as the Spined Soldier Bugs, and parasitic wasps, and maybe spraying with a Neem Oil or pyrethrin based product. Keep in mind that both poisons are broad spectrum and can kill off beneficial as well as pest insects.

Here is a link that might be useful: About Mexican Bean Beetles