Application error occurred during request processing

Hi all,

500 Internal Server Error
Application error occurred during request processing
Details:
com.sap.engine.services.webservices.wsnavigator.WSNavigatorException:
null
Exception id: [0016355ABDF800580000016F00002C7800043D23C1985713]

I get the above exception when I run my webservice. I dont find any
clue to debug my code, becuase i see little/nothing information thrown
by the SAP j2ee engine. I dont get any exceptions while i compile, but
i get this error when i am executing.

i have two classes, which I use as datastructure to return values from
my websevice. Well, i will give you a psuedo code to make you
understand better of what i have right now.

Class klass_1
{
public String var1="";
public String var2="";
....
public ArrayList arrList = new ArrayList();

// setter and getter methods for the above class members.
}

Class klass_2
{
public String var1="";
public String var2="";
....

// setter and getter methods for the above class members.
}

// following is a method in EJB, with that i have created a webservice
public kclass1 method_name(String arg1) throws SQLException{
// PreparedStatement to query database table
// Execute query and get result set values

try{
//instantiate klass1 and set its member with resulted values from
above query
klass1 k1 = new klass();
k1.setMember_k1(result.getString(1));

// Query database with second query statement
// loop through result set you get from the above query
while(result_set.next()){
//instantiate klass2, initialiaze its members with resulted values
from the second query, and add object of klass2 to 'arrList' of klass1

klass2 k2 = new klass2();
k2.setMember_k2(result.getString(1));
....
k1.arrList.add(k2); // This line is giving me problem. }

}catch (SQLException e){
....
}catch (Exception e){
....
}finally{
// close PreparedStatements, ResultSets, and connection obj to db.
return k1;
}
}

i know error-code: 500 occurs when there is problem with source. But
the source compiles successfully. And also if i comment
k1.arrList.add(k2); this line in the above code i execute the
webservice with no problem but i dont get completely what i should
get.

Can somebody help on this?

thank you,
kath.