I am having this problem as well...and I was using the plugin successfully before upgrading to Joomla 1.5.15. The other thing that I am experiencing is that my Google presentation and Joomla Newsfeed will show after several messages:
'the server at administrator requires a user name and password'(Google map will not show after the same message). If I logged on my administrator, then these would work fine.
I uninstalled JSecure last night, got all working without the error message and without logging on administrator. I then reinstalled JSecure (noticing that one file is dated 10/09 - so I uploaded the new JSecure file since my previous file was installed in Sept. 09). Today I am back to the error message.
Again, I uninstalled JSecure, and now I can sign in /administrator AS WELL as /administrator/?my old keyword.
I tried doing this a few times, clearing my cache and clearing my browser history and cache...same results as everyone else. I have not checked mySql table yet, and will let you know if anything changes afterwards.
The kicker is that I cannot find anything in Global Config that asks for permission such as this describes. My site is www.johowdy.com - see if you can get to the directions or the about or the tips from the menu without a password. Thanks!
-----------------------RESOLVED--------------
This is resolved....it was NOT JSecure Auth causing this problem, it was the fact that I had installed a password on my administrator file using a CPanel program called Password Protect. When I removed the password protect lock, all started working correctly with JSecure Auth installed. The previous version of Joomla 1.5.14 worked with JSEcure Auth and the password protect on my administrator file (even though it was a bit redundant, I was trying to enforce many different security measures). Joomla 1.5.15 upgrade is what started the problem, and I placed a question in the Joomla forum as well - to see what is going wrong. At least all is fixed, and Jsecure Auth is working well!