I decided to use captcha + confident technologies really cool system on one of my sites. Immediatley after enabling and logging out i realised i had forgotten to add the line

Site URI:
    https://api.confidenttechnologies.com/vs/customers/dMteQ6pz/sites/my site.com

which sits on top of customer id,site id, API uname and API password... I was in a rush to finish...

After logging out to test and logging back in again, I could not get past captcha. It claimed i made an incorrect entry every time.... then I realised that I was probably in a loop of some sorts. Deleting the captcha and the confident captcha modules using ftp did not fix the problem. Using  /?q=user got an 'access denied' whatever i tried. Then i tried changing $update_free_access = FALSE; to TRUE in settings php but still access denied.  This looked like i had really messed up. But, just on the off chance, I logged on to the site using a different browser ( Epiphany ) and lo and behold I could log in normally! My normal browser is Firefox, and after completely deleting 'history' i was able to logon to the site normally. I must have wasted more than an anxious hour sorting out this problem, caused by being in too much of a hurry.