thought I would post my findings after encountering the infamous 'Invalid token' screen whilst trying to login via Internet Explorer.. through the Front-End of Joomla 1.5.21.
Basically our website was working fine up until a few days ago when we installed a SSL Certificate.
weather that was the cause or not Iam not sure but I personally had no problems logging into the website via Front/back end using (Natively) Firefox. My Users however would be presented with the above named error every-time. This ironically enough was only for the Frontend, as well after accepting the security certificate they could login to the back end no problem.
after wasting some 45minutes in researching the problem and another 30 minutes restoring a backup due to following some geniuses advice in deleting all but the index.html from the /tmp folder and rendering the website useless. *Take Heed* I was then presented with a few issues in the akeeba restore feature which led to internal server errors after I had changed permissions for the installation folder , this was resolved by closing the tab and restating the kickstart from scratch which allowed me to proceed to the next ...next..next...done screens.
there was however a small problem , in which all of the URL's all 3 ticked for SEO,HTML,etc etc in the global configuration screen were not working... Argh!.. what was the problem?... well this version of Kickstart I had set to display a temp restore.html page for others viewing the website during the restore process.. and it had backed up (thank good) my .htaccess file and created it's own. A quick view of the new .htaccess file and aha where's my original one .. there it is , delete the new one rename the old one and Another problem solved.
(worth noting here , that it is also advised to remove all traces of kickstart from your root directory as well)
now after restoring the backup .. from like 3 days ago , another blessing. I noticed that we were using version 1.5.21... This version I assume had a small bug in it which caused IE users to be presented with the error but not FF Users (Myself) in this case.
now since probably 80% of the world uses this crap browser named Internet Explorer I kinda figured that I better get it sorted. Or 80% of Registered users would be thinking .. time to go elsewhere..
easy fix.. in my case..
download and install the update manager for joomla
Then goto components > update manager
update your joomla to 1.5.23 and shes sorted.
hope that helps others.