I've just installed the splunk-4.2.3-105575-x64-release and trying to login using he web browser (ie8) shows a message:
Invalid cookie detected. Try reloading this page or restarting your browser.
What is this? and what can I do about it?
Sorry I only saw this question now -- believe it or not app-owners dont get any kind of notification when people post questions about their apps.
I'm happy to help though. Feel free to email me at email@example.com. Although Splunk support is probably your best bet, I can help you figure out where the problem is coming from.
Do you get the same error with all apps? Any proxy in front of Splunkweb or any weird plugins for browser security? Sometimes things like that will strip custom HTTP headers. It's not inconceivable that this error message is talking about "cookies" a bit erroneously. The problem could be that the splunk session header isn't making it to SplunkWeb and it's default response is to complain about the cookie... Anyway, let me know if I can help.
Are you running other web applications on the same system, so that your browser might be passing cookies for them when it's trying to access Splunk's web interface? If that's the case, try removing those cookies and give it another try.