Thank you for the report. We'll look at that.
We also found that the payment redirection screens were not working with 1.6 so all the online payment plugins are not working currently on 1.6.
You need to change the code
$path = JPATH_PLUGINS .DS.'hikashoppayment'.DS.$name;
to
if(version_compare(JVERSION,'1.6','<')){
$path = JPATH_PLUGINS .DS.'hikashoppayment'.DS.$name;
}else{
$path = JPATH_PLUGINS .DS.'hikashoppayment'.DS.$method->payment_type.DS.$name;
}
in each payment plugin file to fix the problem.