How to reset admin password with drush and Acquia Dev Desktop?
I'm not sure why it's failing for you.
Probably check the error logs to see if there are any warnings or notices being logged there.

The latest versions of drush have drush uli which just gives you a one-time login link for admin.

$ drush uli
http://default/user/reset/1/1311169130/gf-1uDYC51jONONNF-jq3_ciKfLqhE93SsS9YNAnaEY
Unfortunately it doesn't get the hostname right in most cases (probably there's no way to know it if base_url is not set) so you have to change "default" correct hostname.

So in the case above, I would paste the link into a browser and then change it to

http://example.com/user/reset/1/1311169130/gf-1uDYC51jONONNF-jq3_ciKfLqhE93SsS9YNAnaEY
There I have a one-time login link to user 1 on the site. Works flawlessly.

You can also run drush as admin by adding this:

drush -u 1 "command" 

Eg:

drush -u 1 cc all