We could not ping one of our servers. I looked at the event logs and found this entry: Description: The IPSec driver has entered Block mode. IPSec will discard all inbound and outbound TCP/IP network traffic that is not permitted by boot-time IPSec Policy exemptions. Really strange! I did not enable any IPsec policies, the firewall was also disabled on this server. So how did this happen? Well, the server ran out of space and somehow a registry entry got corrupt. Take a look at this KB article. The fix worked for us. Actually the whole key was missing. HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\IPSec\Policy\Local When I registered the DLL , it re-created the key. Reboot…

So, some of our windows servers were showing a logon screen which was blacked out. I mean the logon screen was either totally black or parts of it were blacked out. I still could logon because I could see the cursor and I knew the fields but it sure was a pain! At first I thought it was a video driver issue; but a co-worker showed me this KB article. Basically the subkeys under this registry key somehow get corrupt and need to be recreated: HKEY_USERS\.Default\Control Panel\Colors