JSON.net将C#对象序列化为JSON问题

以下是通过JsonConvert.SerializeObject返回的字符串：

{
    "ComId": "AAAiB+AAHAALOaFAAL","CovId": "AAABC9AAPAAAZYUAAI","EffectiveDate": "/Date(1329368400000-0500)/","ExpirationDate": "/Date(1360990800000-0500)/","State": "TX","DeductibleAmount": 500.0,"DeductibleType": "PD"
}

运行字符串通过JSONLint返回：

Parse error on line 1:
{    "ComId": &
-----^
Expecting 'STRING','}'

下面是我试图序列化成JSON的对象：

public class CommonInfoModel
{
    public virtual string ComId { get; set; }
    public virtual string CovId { get; set; }

    [Display(Name = "Effective Date")]
    public virtual DateTime EffectiveDate { get; set; }

    [Display(Name = "Expiration Date")]
    public virtual DateTime ExpirationDate { get; set; }

    [Display(Name = "State")]
    public virtual string State { get; set; }

    [Display(Name = "Deductible Amount")]
    public virtual decimal DeductibleAmount { get; set; }

    [Display(Name = "Deductible Type")]
    public virtual string DeductibleType { get; set; }
}

我做错了吗？我已经搜索，似乎使用该方法的其他人更干净的字符串！谢谢你提前的时间！