最近遇到一个问题，怎么修改环境网站访问总会报ASP.NET 4.0错

                最近服务器总是会有这样的操作，

导致网站访问不了，

事件的描述是这样的：

Event code: 3005
Event message: An unhandled exception has occurred.
Event time: 2010-12-18 9:55:52
Event time (UTC): 2010-12-18 1:55:52
Event ID: a8a4b55a1f56471b89f85d58b5d56175
Event sequence: 321
Event occurrence: 1
Event detail code: 0
 
Application information:
    Application domain: /LM/W3SVC/685154668/Root-1-129371060758125000
    Trust level: Full
    Application Virtual Path: /
    Application Path: F:websitef-3vshop2
    Machine name: SERVER03
 
Process information:
    Process ID: 1212
    Process name: w3wp.exe
    Account name: NT AUTHORITYNETWORK SERVICE
 
Exception information:
    Exception type: XmlException
    Exception message: Data at the root level is invalid. Line 1, position 1.
   at System.Data.Linq.SqlClient.SqlProvider.Execute(Expression query, QueryInfo queryInfo, IObjectReaderFactory factory, Object[] parentArgs, Object[] userArgs, ICompiledSubQuery[] subQueries, Object lastResult)
   at System.Data.Linq.SqlClient.SqlProvider.ExecuteAll(Expression query, QueryInfo[] queryInfos, IObjectReaderFactory factory, Object[] userArguments, ICompiledSubQuery[] subQueries)
   at System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query)
   at System.Data.Linq.DataQuery`1.System.Linq.IQueryProvider.Execute[S](Expression expression)
   at System.Linq.Queryable.FirstOrDefault[TSource](IQueryable`1 source)
   at F3V.F3VShop2.WebUI.Default.Page_Load(Object sender, EventArgs e)
   at System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e)
   at System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e)
   at System.Web.UI.Control.OnLoad(EventArgs e)
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Page.Proce***equestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

 
 
Request information:
    Request URL: http://*.*.*.*:82/Default.aspx （局域网服务器的IP）
    Request path: /Default.aspx
    User host address: *.*.*.* （访问的机器）
    User: 
    Is authenticated: False
    Authentication Type: 
    Thread account name: NT AUTHORITYNETWORK SERVICE
 
Thread information:
    Thread ID: 14
    Thread account name: NT AUTHORITYNETWORK SERVICE
    Is impersonating: False
    Stack trace:    at System.Data.Linq.SqlClient.SqlProvider.Execute(Expression query, QueryInfo queryInfo, IObjectReaderFactory factory, Object[] parentArgs, Object[] userArgs, ICompiledSubQuery[] subQueries, Object lastResult)
   at System.Data.Linq.SqlClient.SqlProvider.ExecuteAll(Expression query, QueryInfo[] queryInfos, IObjectReaderFactory factory, Object[] userArguments, ICompiledSubQuery[] subQueries)
   at System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query)
   at System.Data.Linq.DataQuery`1.System.Linq.IQueryProvider.Execute[S](Expression expression)
   at System.Linq.Queryable.FirstOrDefault[TSource](IQueryable`1 source)
   at F3V.F3VShop2.WebUI.Default.Page_Load(Object sender, EventArgs e)
   at System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e)
   at System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e)
   at System.Web.UI.Control.OnLoad(EventArgs e)
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Page.Proce***equestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
 
 
Custom event details:
 

结果致使网页无法打开正常的模块！本人是公司的网管，现在老板要求我来学这个asp.net 还没入门。请求大侠们帮助

经过牛人判断，暂时怀疑是数据库的连接缓冲池溢出：

 using (DataContext db = new DataContext())