Taken from this thread.
First make sure:
Under Vista and Windows 7 make sure UAC is disabled:
or else you must set \holdem manager\dbcontrolpanel.exe, holdemmanager.exe and hmhud.exe are started as administrator. Run the windows explorer and navigate to your Holdemmanager installation directory. Right click the executables and select "Run as admin" from the compatibility tab. Windows 7 you MUST set all the executables to always run as admin.
Add exceptions to the windows firewall, even if it is off. If you have a 3rd party firewall, do the equivalent or uninstall it temporarily - http://faq.holdemmanager.com/questio...lems+(Firewall)
Then, do the following if you are still having problems.
1. Right click on HoldemManager\Config\Holdemmanager.config
2. Click properties
3. Click security tab
4. Click edit
5. Click add
6. Click advanced
7. Click find now
8. Find the user you are logged in as
9. Click OK
10. Make sure all the boxes read / write / edit for that user