No mapping between account names and security IDs was done

hi -

i added a custom MicroStrategy webpart to my site.  When I modified the webpart and added 'Guest' in the credential field, I get the following error:

"No mapping between account names and security IDs was done"

Looking further in the ULS logs I found the information below.   Any ideas?

UserPicker.GetUserPropCollectionByAccountName(). It could be due to Non_AD environment: System.ComponentModel.Win32Exception: No mapping between account names and security IDs was done     at Microsoft.Office.Server.Utilities.Win32.AdvApi.LookupAccountName(String lpSystemName, String lpAccountName, IntPtr Sid, Int32& cbSid, StringBuilder ReferencedDomainName, Int32& cchReferencedDomainName, SID_NAME_USE& peUse)     at Microsoft.Office.Server.UserProfiles.UserProfileGlobal.GetSidFromAccount(String strAccountName, SID_NAME_USE[] IntendedAccountType, SID_NAME_USE& sidUse)     at Microsoft.Office.Server.UserProfiles.DS.GetUserPropCollectionByAccountName(String strAccountName, UserFormat unt).