JSON odata error - Bad Request. Bad syntax or something else?

I can't seem to egt the data I need with our JSON script in our CRM environment.

The script looks like this:

function SetMedlemsgrupp() {
    try {
        var utbildning = Xrm.Page.getAttribute('stc_utbildning_id').getValue();
        if (utbildning != null) {
            $.ajax({
                type: "GET",
                contentType: "application/json; charset=utf-8",
                datatype: "json",
                url: '/JUTVECKLING/XRMServices/2011/Organization.svc/stc_utbildningSet(guid\'' + utbildning[0].id + '\')?$select=stc_medlemsgrupp_id',
                beforeSend: function (XMLHttpRequest) {
                    XMLHttpRequest.setRequestHeader("Accept", "application/json");
                },
                success: function (data, textStatus, XmlHttpRequest) {
                    var medlemsgrupp = data.d.stc_medlemsgrupp_id;
                    if (medlemsgrupp != null) {
                        var medlemsgruppLookup = Xrm.Page.getAttribute('stc_medlemsgrupp_id');
                        medlemsgruppLookup.setValue([{ id: medlemsgrupp.Id, name: medlemsgrupp.Name, entityType: medlemsgrupp.LogicalName }]);
                    }
                },
                error: function (XmlHttpRequest, textStatus, errorThrown) {
                    alert('Odata select failed, status: [' + textStatus + '], error: [' + errorThrown + ']');
                }
            });
        }
    }
    catch (e) {
        alert(e.toString());
    }
}

What I get in response is "Bad Request". I can connect to the same URL with LINQpad so I know its reachable and that the params exists.

Is the syntax wrong or does anyone have any idea what might be the problem?

Regards

Linus