I just got a new Lenovo laptop running Windows 7 Pro 64 Bit with Service Pack 1. I have installed all Win 7 Updates. When I try to connect to other Windows 7 Ultimate (32 bit) desktops through Remote Desktop Connection over my LAN, I get the following error: "An authentication error has occurred. The requested security package does not exist" I can connect to a Windows Small Business Server 2003 32 bit server from the laptop without problem. All machines are members of the same Windows domain. The Windows 7 machines I am trying to connect to can connect to each other without issue. NLA is set as not required on each of the desktops, though I have tried turning the NLA setting on, and received the same error. I have even tried running the 32 bit version of mstsc.exe and disabling the 64 bit version as discussed here: http://www.davidmoore.info/2009/12/02/running-32-bit-remote-desktop-connection-on-windows-64-bit/ This had no effect either.

Did you try disabling the firewall?

Windows firewall is disabled on all machines. As I mentioned, the other 32 bit machines can connect to each other over the LAN just fine, so it can't be a firewall issue anyway. I'm thinking it's a 32 bit vs 64 bit problem but none of the solutions I have found through searches work for me. I'm thinking about installing the 32 bit version of Win 7, but it's such a pain to download and install all of the Lenovo specific drivers and utilities that I was hoping to avoid that. Hopefully someone here can provide some insights before I resort to the "nuclear option."

Hi, Based on my research, please check whether the value of HKLM\SYSTEM\CurrentControlSet\Control\Lsa\Security Packages is kerberos msv1_0 schannel wdigest tspkg pku2u If not, please correct it and see how it works. Note: Serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, please refer to How to back up and restore the registry in Windows. Hope this helps. Jeremy Wu TechNet Community Support

Jeremy, you're a genius. That worked like a charm. The last two entries were missing. I'm curious as to why the registry was missing these entries, but I guess, as "they" often say, "Why ask why?" I can now connect to from the Win7-64 machine via remote desktop. Your help is much appreciated. Todd Qualls

Nice job Jeremy- I too had a client with a brand new Lenovo Edge laptop, was getting this error after we configured a couple RDP connections. Checked the registry key you posted, and found it was missing the tspkg and pku2u entries. Added them, rebooted (just because) and voila! Thanks for your help!