C#

CreditCardStruct CCStruct = new CreditCardStruct( ); 
if (_ProcAuthorizationWeb(ref CCStruct))
{
  Console.Writeline(CCStruct);
}

1. You probably get the error message for files your program was using? check that each of your threads closes each file it uses when it's done with it.
2. Closing all processes that accessed some file doesn't seem to be a healthy idea to me. Especially if u can insert any file name. If the problem is with specific files, maybe you should go the other way around, and inherit a "file" class to alert you (by an event) when it is accessed and by whom (which process)
   

<code>
[WebMethod(Description="Login Operation")]
public string Login(string userName,string password)
{
HttpWebRequest req = (HttpWebRequest) HttpWebRequest.Create("http://[www.desiredsite.com/login.aspx?name="+userName+"&password="+passWord)
req.KeepAlive = false;
HttpWebResponse resp = (HttpWebResponse) req.GetResponse();			
StreamReader sr = new StreamReader(resp.GetResponseStream(), System.Text.Encoding.UTF8);	
string all = sr.ReadToEnd();//So far you send the info, thus you get string having the result page 
...//In these lines of code , regarding to the html structure, you should wrap the info you need
...// clean up the unnecessary tags and find whether the login is succeeded or not by manipulating html
...
return resultString;//This will be the web service's respond string to the application.
</code>