Transaction (Process ID 83) Was Deadlocked

Hi,
I got the following error when I try running my “comments.aspx� page with visual studio 2005Exception Details: System.Data.SqlClient.SqlException: Transaction (Process ID 83) was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Rerun the transaction.

      fExecuteQuery(String commandText, String dataSetName) +90   fExecuteQuerySet(String commandText, String dataSetName) +36   ASP.comments_aspx.GetNarComment() +618   ASP.comments_aspx.Page_Load(Object sender, EventArgs e) +476   System.Web.UI.Control.OnLoad(EventArgs e) +67   System.Web.UI.BasePage.OnLoad(EventArgs e) +1013   System.Web.UI.PopupPage.OnLoad(EventArgs e) +4   System.Web.UI.Control.LoadRecursive() +35
       System.Web.UI.Page.ProcessRequestMain() +750

The segment code was the problem sits in file "comments.aspx"::
…
string cmdText=��;
       
cmdText = string.Format(@"-- Get All Narative comments fo all students in the course from @selectedTermID down to its child terms
                    exec aagGetStudentSectionComments @companyID={0}, @sectionID={1}, @selectedTermID={2}, @StudentID={3}                                                                                                 
                    ", _companyID, sectionID, selectedTermID, studentID);
 
ds = fExecuteQuerySet(cmdText, "getMySet");
       
…
// the 2 functions to deal with ADO.NET to be called in above code segment
 
// return a dataset.
                   public DataSet fExecuteQuery(string commandText, string dataSetName)
                   {
                             DataSet mds = new DataSet();
                             SqlDataAdapter da = new SqlDataAdapter(commandText, _cn);
                             da.SelectCommand.CommandTimeout = 600; // 600 seconds
                             da.Fill(mds, dataSetName);
                             return mds; // return dataset
                   }
                   // Assume para commandText contains sql query which returns a table or more.
                   // return a DataSet.
                   public DataSet fExecuteQuerySet(string commandText, string dataSetName)
                   {
                             DataSet mds = new DataSet();
                             mds = fExecuteQuery(commandText, dataSetName);
                             return mds; // return DataSet
                   }
 
Please give me the reason why that dealock happens?
Thanks in advance