The answer to the beans not growing well is apparently the salt levels here.
Malcolm Campbell says that our water supply coupled with salt levels in the soil are too high for beans, especially dwarf ones, to grow well here.
I'm on River Murray water here and it's quite bad this year. My tomatoes are showing signs of too much salt as well this year.
When we had Malcolm Campbell speak at a garden club function in 2002 he said not to even bother trying to grow Dwarf Beans in our area of SA!!
In this link from Gardening Australia (click on it to be taken there) he explains a lot of facts about the salinity levels and evaporation rates that is quite interesting to those of us in hotter dryer areas of Australia.
He gives some useful hints on how to combat the effects with mulch and shade. Also which vegetables and trees to plant that tolerate high salt levels better.
I wanted to trial different types of beans, mainly stringless varieties, this year and they failed so I will go back to the Blue Lake or Purple King climbing ones next year to hopefully get a decent crop. These varieties have done well in my garden before.