On the LT that your using, is there any 3rd party firewall or Antivirus programs running? Do you have windows firewall ON? It sounds like everything except yahoo videos is not working, might be a web site issue maybe.
What Windows version are you using?
I would turn off all security programs temporarily and test.
What browser are you using? Try a different one like Opera or FF and see if they exhibit the same results.
Do you have a different PC that you an test on the same network and does it exhibit the same results?
Try directly connected to the ISP modem and see if the PC exhibits the same results.
Keep us posted.