Hi,
Echolife HG 520b
This is a cheap router supplied by TalkTalk.
I had a similar one that kept dropping the connection - I replaced the router.
If you have had this router a while I would be tempted to replace it.
You could always contact TalkTalk and ask them if it would be possible to replace it.
The setup info is here:
http://help.talktalk.co.uk/app/answers/detail/a_id/1607/~/wired-connection-setup-for-huawei-echolife-hg520b
The router IP Address is 192.168.1.1
From your ping details - you could not ping the router at all when the connection was down.
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I suspect you may need to replace the router - but try the following when there is no connection......
ping 127.0.0.1
This will confirm if the TCP/IP is OK.
This should complete even if there is no connection.
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Another possibility is the wireless adapter - but an intermittent fault is rare.