I get the following error when trying to access a controller Method from a VisualForce page: Visualforce Remoting Exception: only whitespace content allowed before start tag and not C (position: START_DOCUMENT seen C... @1:1)

Here is the Controller Class:

    @RemoteAction
    global static String saveUser(Credentials__c cred, Contact con) {
    	
    	cred.Lead_Number__c = integer.valueof(cred.Lead_Number__c);
        
        Http h = new Http();
        
/*
Initialize endpoint URL here
Code not included but works
*/
        
        HttpRequest req = new HttpRequest();
        req.setEndpoint(url);
        req.setMethod('GET');
        
        HttpResponse res = h.send(req);
        Dom.Document doc = res.getBodyDocument();
        DOM.XMLNode root = doc.getRootElement();
        //Parses returned XML to String
        String result = Global_Methods.walkThrough(root);
        return (result.length()>0 ? result:'Error');
    }

And here is my call from the VisualForce Page:

		Global_Methods.saveUser(rec,con, function(result, event){
			var res = result.split(",",2);
			res[0] = parseInt(res[0]);
			if(res[0]!=1){
			alert(res[1]);
			    deleteId(record.Id);
			    return false;
			}
			else {
				RegisterTrial(con,rec,subProducts,type);
			}
		}, {escape:true});

The odd thing is that this works fine from a different VF page. I have no idea what this error means or how to fix it. Any insight is very much apprechiated. Thanks!