Annoying Windows message that cannot be closed

Hello, I recently purchased (about 3 weeks) a new PC running Vista. I have
been tweaking this machine for a few weeks and now I have a new issue. For
approximately 4-5 days now I receive sporadically (maybe once and hour) a
message box that states "Navigation to the webpage was cancelled" Then it
continues, "what you can try?" "refresh the page" The strangest thing to me
is that the message box does not contain the classic X for closing the
Window, I have to use task manager to dispose of the message box. To me,
this is a bug since I don't feel Windows (or any OS) should throw any errors
or informational messages that can't be disposed of. With that aside can
anyone tell me what this could be? I assume some program is doing something
in the backround to cause this but I am not sure what it could be and it is
somewhat annoying dealing with these messages.

Thanks

David