Error: Cannot Generate SSPI context

When someone tries to connect to a SQL Server instance, the error shows up: > It's not possible do generate SSPI context. Yesterday we had a blackout (don't know how to say this expression in English) and I had to shut down our servers. Looking for answers, I found this: SQL Server 2008 connectivity issue : cannot generate SSPI context But it doesn't help me, because they're working fine until yesterday. I don't want to change anything. But if a have to, I will change it. Obs: I can't restart the server now. --- Edit: Since I my answer, we haven't had any errors.