You didn't say how your PC is connected to the router.
You might try unplugging everything that's connected to your router (other than TV and PC) to see if that makes a difference. i.e. some other networked device might be interfering.
Also, wireless connections tend to be unreliable both because signal strength can vary (depending on where people and other obstructing objects are) and RF interference from other devices can cause problems. In particular, some cordless phones use the same frequency range. Another possibility is that your neighbors installed their own wireless networks, conflicting with yours.
Marantz SR7009/7.1.4/FH+TM/DefTech PM1000/LCR+TM amped