Thread disrupting execution of ASP.net main application - asp.net

Question

I have an ASP.net web app that spawns a process (in a thread). This thread calls a '.dll' to connect to another 'subsystem'.
Problem is, when there are errors connecting to the 'subsystem', it affects my main application (main UI) and I get a 'connection refused message'. I have already put in 'try-catch' error handling routines in my thread. FYI, I would like to treat the thread as a 'Fire and forget' thread.
The thread is spawned when btnSubmit is clicked.
Please refer to trimmed-down extract of code.
protected void btnSubmit_Click(object sender, EventArgs e)
{
try
{
txt_hide.Value = sStatus;
if (sStatus == "")
{
//create thread for posting
id = Guid.NewGuid();
Thread th = new Thread(() => postXMLClass.PostXML(sSeqNo));
th.Start();
sStatus = "Transaction generated..please check posting status..";
lblMessage.Text = "Transaction Generated...";
}
else
{
FormView1.DataBind(); //refresh the form
clib.Show2("Error generating transaction : " + sStatus, sender);
lblMessage.Text = "Error generating transaction : " + sStatus;
}
}
catch (SqlException ex)
{
lblMessage.Text = "Error generating transaction ...: " + ex.Message;
}
catch (Exception ex)
{
//sqc.Transaction.Rollback();
lblMessage.Text = "Error encountered...: " + ex.Message;
throw;
}
finally
{
if (dbc != null) dbc.Dispose();
if (clib != null) clib.Dispose();
}
}
public static void PostXML(string inlinkcode)
{
string sToken = "", sXMLOut = "";
Xml.Router.XMLRouter cX = new Xml.Router.XMLRouter();
try
{
cX.set_Options("com.xml.router.nameServer", appSetArray[0]);
cX.set_Options("com.xml.router.nameServerPort", appSetArray[2]);
cX.set_Options("com.xml.router.logicalServerName", appSetArray[1]);
{
sLinkcode = inlinkcode;
if (sLinkcode != null && sLinkcode != "")
{
strxml = "<?xml version=\"1.0\" encoding='UTF-8' ?>";
strxml += "<TableLinkRequest version=\"1.0\"><DocumentLinkStart><Request><StartParams>";
strxml += "<CmpCode>X</CmpCode><DocCode></DocCode></TableLinkRequest>";
sXMLOut = cX.Send(sToken, strxml);
}
}
}
catch (Exception ex)
{
Console.WriteLine("Exception {0}", ex.Message);
}
finally
{
if (cX != null) cX.Logoff(sToken);
}
}