I was trying to connect from primary test box to my hyperv core test box via the Hyper-V MMC management tools, I kept getting "Access denied. Unable to establish communication between Client and Server".
From the command prompt of your ‘Client’ can do this by typing: ”DCOMCNFG” in the run-command in Windows.
2. Browse trough to: “Component Services > Computers > My Computer”.
3. Open Properties for “My Computer” and select the COM Security tab.
4. In “Access Permissions” area click the “Edit Limits”-button.
5. Select the “Anonymous Logon”-group and make sure the “Remote Access” is set to Allowed.
Now you client tools should connect successfully to the servers Hyper-V management.
danielheth 
Thanks Daniel!
This was a far easier solution than another one I found that required executing a number of command line commands.
Tim
That worked perfect! Thanks Daniel!
This is my second highest rated blog post… could you guys let me know about your projects… maybe i can point you into new directions or post additional related content.
Thanks! This was driving me nuts, as I knew the servers were running, but restarting let me back into management. I figured it was some kind of permission.
Excellent Post!!!
I was finding this solutions for months!!!!
Excellent!
I have this problem for a while and found several solutions that require modifying settings on servers. This solution was the simplest and easier without touching anything out there. Thank you!
http://blogs.technet.com/b/jhoward/archive/2008/08/07/hyper-v-why-does-hyper-v-manager-not-always-work-over-vpn-connection-access-denied-or-rpc-server-unavailable-errors.aspx
Although you fix didn’t work for me this did.
It also talks about your fix.
My solution:
Cleared out DNS for rogue entries to my laptop.
ipconfig /flushdns on each server to restore connectivity.
Thanks for sharing though.
This didn’t work for me. The funny thing is, sometimes the Hyper-V works and other times it doesn’t. I am running Hyper-V Server 2008 RC2 (standalone) and using Hyper-V Manager for Vista 64x.
This is my first time running any sort of virtual environment in Windows and it is very frustrating!
Thanks for that. It was quite an irritating error. 🙂
Thank you for linking to my site. Feel free to ask questions… i’ll help with anything i can.
This solution came from an intensive try-fail-try again session… Glad i could help.
Since this post and your comment i’ve setup a full server using Hyper-V. I’m extremely happy with the February SP1 update. Its added dynamic capabilities and thus i can get more VM’s on then ever before.
Not sure if this matters, but i’ve recently setup a reverse dns and it’s done wonders to my whole networks ability to communicate. The network as a whole works faster and i believe my latest Hyper-v server is working better than my previous tests as a result.
Really glad i could help Renzo.
worked for me, thanks very much – seems very insecure to have to open up COM security to allowed for ‘anonymous’ though ?
I had two lines of thoughts on that dredders,
1. Opening it up this way is to get it to a point of working, and since it’s on an internal private protected network i wasn’t to worried about security.
2. Once it is working, then we can slowly tighten security down which i believe is easier to do than loosening it up.
Thanks for bringing this up, I’ve been growing more and more security aware and i’m working on an update for this article on tightening security.
Your tips is awesome…and here I thought it was a server thing…Thank you…
Thank you that helped me resolve my remote hyper-v connectivity issue.
Eliminating that one step saves considerable time over time.