myarr[0]=11111&myarr[1]=22222
Then a controller that takes IEnumerable
Looks like the default binder in Openrasta behaves a bit differently. You need to format your form data like this instead :
myarr:0=11111&myarr:1=22222
This works with posting/putting arrays of objects as well (ie myarr:0.Name=Dave), aswell as being supported in posting/putting models which contain arrays within them