I used hamachi once in the past, but a friend wanted me to use hamachi, so I uninstalled and downloaded the new version. However, it won't let me go online, and the "Attach to LogMeIn account", the creating/joining network options are grayed out. It flashes to connecting, then logging in, then back to offline, and then it gives me this message:
I had the same problem and contacted the helpdesk about this problem.
The sollution which is listed below solved the problem straight away.
This would typically occur when upgrading from Hamachi to Hamachi2. Please uninstall Hamachi2, removing all user preferences, and then reinstall to acquire a new IP Address and Client ID. If you removed Hamachi prior to installing the current client, then the settings still remained.
I spent a couple hours trying to fix the same error (The Hamachi server has denied your login request) on my Vista computer after updating to the new version of Hamachi. I tried all the suggestions here and from logmeinwiki.com article and from several other forums out there I found on Google. Although the only thing that ended up fixing my issue was to run a Search in Vista including all system files and unarchived files for "hamachi". This is after uninstalling Hamachi and rebooting by the way. It found several different Hamachi drivers in the Driver folder. You have to add yourself to the folder that contains the drivers and give yourself full rights in order to delete the folder. After that everything worked fine.
I hope this helps someone in the future when there seems to be no end to the problem.
The fix i found was to uninstall whatever version you have installed. Then reinstall it using the latest installer. At one point there is a check mark during the installer that will ask something along the lines of "apply these settings" referring to importing found settings. Uncheck this check mark and let hamachi finish installing. Once you finish it pops up like brand new.
FYI: I had done the uninstall with remove all user's settings.
I have BT NetProtect Plus for Vista and I added the Hamachi shortcut to the list of program permissions and nothing happened. This is because when I installed Hamachi it automatically added a program to the list of program permissions. It's called Hamachi2 Client Tunneling Engine. This was set to block.
You should set this to full access or whatever allows full internet connection so that it can connect to the Hamachi servers if you have a firewall.
I hope this helps anyone who has the same problem with BT NetProtect Plus as I did.