Link>
Welcome!What region are you located?
What ISP Modem make and model do you have?
Has a Factory Reset been performed after the FW was updated?
Some things to try:
What wireless modes are you using? Under Setup/Wireless/Manual.
Try single mode G or mixed G and N on 2.4Ghz and single mode N on 5Ghz?
Try setting a manual channel to a open or unused channel. 1, 6 or 11. 11 for single mode N if the channel is clear.
What security mode are you using? Preferred security is WPA-Personal. WPA2/AES Only. Some WiFi adapters don't support AES, so you might want to try TPIK only or Auto.
What wireless devices do you have connected?
Any cordless house phones?
Any other WiFi routers in the area? Link> Use
InSSIDer to find out. How many?
Turn off WISH, and WPS under Advanced.
Try turning off Short GI, WLAN Partition,and Extra Wireless Protection if you have it. Under Advanced/Advanced Wireless.
Enable
WMM Enable Under Advanced/Advanced Wireless.
Also be aware that there are antenna differences between the 857 and 815, mainly external antennas vs internal...