Outlook 2000 SP3 Help

Been using this client for several years to take care of my personal and business e-mail. Recently the program has taken to giving me server denial errors when trying to get new mail from both my Yahoo and Gmail accounts. If I shut Outlook down and restart it, it runs fine again for an indefinite time (hours usually) before I need to reset yet again. I’ve tried using the “Outlook Repair” utility to no avail. Anyone have a clue what could be causing this?
TY