ok, i noticed this awhile back too, but I discovered something.
if you go to
http://www.stormtrack.org/
and then you enter your username and password and click the stay signed in box, it won't stay signed in.
but if you click on Forum or go directly to
http://www.stormtrack.org/forum/
and then enter username and password and check the sign-on box, it will stay signed in.
There's an option on the Admin side (i recall from helping a couple other forums), but I can't remember exactly where it is, without seeing the admin control panel, but checking a certain box will correct the issue.