We're sorry. We ran into a problem completing your request. Please try that again in a few minutes

If you insert your Excel Web Access and then you choose the workbook from a trusted document library you may have this error:
We’re sorry. We ran into a problem completing your request. Please try that again in a few minutes.

to fix this issue

1.   Open Central administration

2.   Application management

3.   Manage web applications

4.   Select the web application where your site 

5.   Manage service connections

6.   Select the Excel Services Application

7.   Click OK

if your have already configured your Excel Services (ref: http://technet.microsoft.com/en-us/library/jj219698(v=office.15).aspx) Everything will be OK.

Enjoy...

Error: Only machine administrators are allowed to create administration service job definitions of type: Microsoft.SharePoint.Administration.SPSolutionDeploymentJobDefinition

When I'm trying to deploy a custom SharePoint 2013 solution to my Test Farm using a PowerShell script I received the Folowing error :
Access denied.  Only machine administrators are allowed to create administration service job definitions of type: Microsoft.SharePoint.Administration.SPSolutionDeploymentJobDefinition, Microsoft.SharePoint, Version=14.0.0.0, Culture=neutral, PublicKeyToken=.....

To fix this issue in Windows Server 2012 : you need to turn off UAC (User Account Control) via registry by changing the DWORD "EnableLUA" from 1 to 0 in "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system".

 You will get a notification that a reboot is required. After the reboot, UAC is disabled.

The error is fixed.

Read about UAC in TechNet.