February 20, 2016
The usual procedure:
1) step 1 >> disabled the cache in "Cache Management"
2) installed the module (extension)
3) logged-out from the admin
4) logged-in back into admin
5) flushed the cache
went to orders and deleted the test orders easily (as promised).
everything works as a charm.
6) re-enabled the cache
.. back to work.
thank you for a very, very useful and free extension,
p.s. using Magento CE ver. 220.127.116.11