This message do not really indicates what happened to your SharePoint. You just get the date and time, a Correlation ID and an explicit description saying: "An unexpected error has occurred".
What to do with about these information? How tot get more details? There are several solutions that you can you find in this article.
LOGS files
This method allows you to get more information about an error by reading the SharePoint log files. To do so, we will explore the SharePoint Hive by connecting on the server causing the error (and do not forget to write down the date, the time and the Correlation ID GUID, they will be useful later on).
When you are connected remotely to the server, open the Hive folder by following this URL:
c:\Program Files\Common Files\Microsoft Share\Web Server Extension\14
Regarding the SharePoint version, the last number change. In SharePoint 2007, we use the number 12, in SharePoint 2010, the number 14 and in 2013 the 15.
Now, we are in the Hive.
Within this folder, open the LOGS folder to display all the SharePoint logs of the server.
Attention, if your SharePoint farm contains more than one server (eg. several front-ends using NLB), you have to check the logs files on all these servers.
Regarding the date and time, open the log file containing the error. As this one occurred at 7.58 am, we will take the file created at 7.53 am and modified last time at 8.01 am. Within this file, we will search for the GUID from the Correlation ID:
And here is the error message you were looking for.
PowerShell script (SharePoint 2010 and 2013 only)
This second method consists in asking SharePoint to give us the error message using a PowerShell command.
Here is the command:
get-splogevent | ?{$_Correlation -eq "7cd48C88-0fa8-4143-88b5-c311caecf34f" }
And the result:
And if you want to get the complete error message, try the following:
get-splogevent | ?{$_Correlation -eq "7cd48C88-0fa8-4143-88b5-c311caecf34f" } | select message | Format-List
Which gives you:
For more details about this amazing (but a bit slow) command, I recommend you the following TechNet article from Microsoft: Get-SpLogEvent article.
SQL Server request or by development
If you want to find the error message using a SQL request or by code, I recommend you the great blog from Tobiaz Zimmergren, and mainly this article.