Recently we investigated issues where non-admin users could not open Powerpivot 2012 window in Excel 2010 on Windows XP machines.
When trying to open the Powerpivot window they get the following error message:
“Embedded Analysis Services Engine: Could not open embedded Powerpivot data”
During the investigation it turned out that the "SeIncreaseBasePriorityPrivilege" windows privilege is required for opening the Powerpivot window.
Users that have this privilege won't have issues in opening Powerpivot window anymore.
Unfortunately only administrators have this privilege by default on Windows XP.
But administrators can assign the privilege to users or groups that need to work with Powerpivot via the "User rights assignment" folder in the Local Security Policy (secpol.msc) tool.
Alternatively roll it out to all domain machines via group policy.
A KB article explaing the issue is on the way and we hope to have a Hotfix available soon.
July 2012 update:
We noted that the issue is not limited to Windows XP, but can affect Windows Vista and Windows 7 clients as well.
The difference being that on these newer operating systems you should be able to use Powerpivot with non-admin users unless you remove privileges that were granted by default.
On Windows Vista and Windows 7 the privilege required for usage of the Powerpivot window is "SeIncreaseWorkingSetPrivilege".
While office programs will be (and should be) primarily used on client operating systems, Powerpivot usage on the corresponding server operating systems (Windows Server 2003, Windows Server 2008, Windows Server 2008 R2) has similar issues.
You can avoid the described privilege issues by downloading the Powerpivot add-in from cumulative update 2 for SQL Server 2012: http://support.microsoft.com/kb/2703275
The 64 bit add-in is available as "2012_RTM_PPExcel_CU2_2703275_11_0_2325_x64", the 32 bit add-in as "2012_RTM_PPExcel_CU2_2703275_11_0_2325_x86".