I did some searching and I couldn't find the solution...
We have a dedicated machine with Outlook 2007 publishing a company calendar. Each employee is subscribed to that calendar via Outlook 2007 or Outlook 2010. About a few weeks ago, 10 or so employees started to get the username and pw prompt in Outlook to access the subscribed calendar. They would enter their credentials and put a check mark next to remember my credentials, but it would keep popping up.
I logged on to the machine publishing the calendar and tried to re-publish the calendar, and I got an error message stating it wasn't able to reach the server. (I made sure that the machine has stable internet connection)
The only thing I got from some research was that same symptoms were observed back in 2008 and 2009 when the server on the Microsoft side was acting up.
I would greatly appreciate any input on this issue.