Threading are self-abortingm why and how

Question

I use a simple thread t = new thread() and start it with t.start(function); It rans nice for about 20-25 minutes and are then aborting.. why? I have no error codes and can't write any output in catch.. May it be a problem that the t.start(function) calls a interface with functionname.Save() ? The thread is called by click a button on a web page. When I try this on my asp.net developer webserver it rans fine,