I can't find any documentation on this result

I'm getting when reviewing what's going on in my Salesforce.com System Log.

An ambiguous: "Interal Salesforce.com Error" is listed as the status of the operation: "APEXSOAP"

Furthermore, when I review the SOAP Response on the other end, I am getting a SOAP Fault message: "No Visualforce context has been established", since SOAP Faults Map to Exceptions -

I'm assuming I have an 'Exception somewhere in my code, except:

 As far as I know this issue is only happening on instances of 'na1' (as they have already had the Spring '11 Release Installed)...

Thoughts?

Update: The culperate seems to be a SOQL Query within a 'StandardSetController', the query is a pretty straight forward StandardSetController, similar to the following:

Serialization error at runtime?

transient public ApexPages.StandardSetController con { get; set; } //Serializable
public ApexPages.StandardSetController GetCon() {
if(this.con == null) {
this.con = new ApexPages.StandardSetController(Database.getQueryLocator([Select Id, Name, A_Custom_Field__c FROM Campaign ORDER BY Name limit 2000]));
	// sets the number of records in each page set
	this.con.setPageSize(200);
	}
	return con;
	}