Well everything was well working with AD then change to forms authentication ,

""Unable to delegate credentials. Please modify Excel Services configuration to be consistent with Windows SharePoint Server

[User: fbaMembers:xxxxx].""

This issue happen when i use Excel Services with Forms authentication in a Farm.

To correct  this issue i change the SSP shared Services to TrustedSubsystem is the default value in a Windows server farm.

stsadm -o set-ecssecurity -ssp sharedservices1 -accessmodel trustedsubsystem

stsadm -o execadmsvcjobs

iisreset 

Set-ecssecurity: Stsadm operation (Office SharePoint Server)

http://technet.microsoft.com/en-us/library/cc263284.aspx

After this start access to Data withou authentication problems.

Hope this help...