I was also encountering a similar problem on my site. I had upgraded from 1.013 to 1.0.14RC1. I was able to log into the Admin but was getting kicked out every few minutes and getting the Invalid Session message. This is what I did and resolved my problem:
1. When I was logged in the Admin area I clicked on
System > System Info then clicked on
System Info tab. I noticed that under
Session save path the value was
none. I also clicked on the
Permissions tab and noticed that the
Session Directory was
Unwriteable.
2. I then
created the following directory in my joomla root and named it
session and set
permissions to 7553. I logged into my hosting control panel and located my
php.ini file. (I have PHP 5)
4. In the php.ini file I found the line
session.save_path = " /tmp"5. I
uncommented the line
6. I changed the /tmp to
"absolute_path_to_my_web_document_root/htdocs/session" (replace with your absolute path and the name of the folder you created for your sessions in step 2) then
Save.
7. I returned to my Joomla admin and was able to log in with no problem. I went back to the System >Sytem Info page and now I have my session save path value and also on the Permissions tab the Session Directory is writeable.
If you have the following directory in your hosting root
/cgi-bin/tmp you can also use this as your session save path directory instead of creating the session folder in step 2. So your step six would be
absolute_path_to_my_web_document_root/cgi-bin/tmpAnd that's my contribution to the world today
