Function hangs when called from a windows service

Hi guys,
Please help!!!! I have a function that I am calling to automate processing of invoices. Most of the times this function works without issues but from time to time it hangs. i.e.
Here is the function:

public void ProcessInvoices()
        {
            bool rt = true;
            try
            {
                rt = CaptureAllInvoices();
                if (rt)
                {

                        Write2ErrLog("------Email Invoices Started-" + DateTime.Now);
                        this.EmailInvoices();
                        Write2ErrLog("------Email Invoices Completed-" + DateTime.Now);


                        Write2ErrLog("------Email Single Invoices Started-" + DateTime.Now);
                        this.EmailSingleInvoices();
                        Write2ErrLog("------Email Single Invoices Completed-" + DateTime.Now);

                        Write2ErrLog("------Fax Invoices Started-" + DateTime.Now);
                        this.FaxInvoices(false);
                        Write2ErrLog("------Fax Invoices Completed-" + DateTime.Now);

                }
            }
            catch (Exception ex)
            {
                Write2ErrLog("---------Error in Process invoices: " + ex.Message);
            }
        }

So it gets to this.EmailInvoices() and starts processing email but stops on the first one and doesn't move to the next function call.

Please advice on an approach I can take to troubleshoot this issue. I use try catch in all my functions but nothing is being caught.

Thanks in advance

Sam

Tags: C#, Threads