-= Apologies for the brevity here, I only had time for a quick post but wanted to get the pertinent points published.
I have run into a situation recently where I needed to lookup a group name from a list, and had issues translating the claims formatting group name returned within SharePoint 2010.
Consider the following scenario, you have a custom list which contains a series of references in one column, and a security group which you wish to select from the standard people picker.
If you use the Query List action within Nintex to obtain the associated security group for the desired reference, you may note that you see a group name of the following format:
c:0+.w|s-1-1-11-111111111-1111111111-111111111-1111
This can be translated using an LDAP query with the following key parameters:
Query: (&(ObjectClass=Group)(ObjectSID=s-1-1-11-111111111-1111111111-111111111-1111))
-= where s-1-1-11-111111111-1111111111-111111111-1111 is your group SID returned from querying your list.
Property to retrieve: Name
There you go, you should hopefully be able to easily retrieve the readable group name from the above.
I have not verified all of the scenarios where this may be of use (nor whether I’ve actually done something in error to even need to apply this workaround), I’m using claims based authentication in my environment.