I'm not sure if this is an issue with HS or VFB, but when I enable views filter block for my view, and submit a filter, I get a no content found response, without HS everything works, with out VFB everything works.
This is the url I get when I submit a filter with views multiblock...
http://test.jony.net/trees/all?filter0[hierarchical_select][selects][0]=20&filter0[hierarchical_select][selects][1]=label_1&hs_form_build_id=hs_form_633b1597c776b785a4f2d00f4c895b26&formsingle_token=4290dbf3b01b4fdd1650848154edc5e7&form_id=views_filterblock
this is what I get with the same filter settings, with out views filter block enabled
http://test.jony.net/trees/all?filter0[]=20&formsingle_token=a44bdf080f8c110c75767dadb64bd8e6