Threading problem

[C# Programming]

hi everyone, http://www.barakasoft.com/script/Forums/Images/smiley_shucks.gif
i have a code like this:

if (condition == true)
{
Thread t = new Thread(new ParameterizedThreadStart(Func));
t.Start(param);
}

.
.
.
//and func is:
Func(Object o)
{
Form1 form = new Form1(o);
form.Visible = true;
}

but when the thread starts, my form appears and suddenly it disappears http://www.barakasoft.com/script/Forums/Images/smiley_frown.gif . it seems thread ends the form process. what should i do? http://www.barakasoft.com/script/Forums/Images/smiley_tongue.gif

thanks in advanced