Loss of Broadband kills Wireless on 2710n

Last night I lost my Internet connection. The router was still syncing but PPPaA wouldn't reconnect so I rebooted the router.<br/>
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When the 2710n restarted, PPPoA still couldn't negotiate the login so kept trying. The router was syncing OK but after about a minute wireless turned off. When I checked my wireless settings via the web i/f everything was as it should be so I clicked on OK which restarted wireless - for approx another minute - then it went off again. Which is all very well, but my LAN has a server on it and I couldn't access it from my laptop wirelessly. No matter what I did I couldn't keep wireless running, apparently because the router hadn't connected to broadband.<br/>
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What's going on with this? Why won't wireless work irrespective of whether I'm connected to my WAN? Is this a "feature" of the 2710n?<br/>
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BTW, the router came with 3.3.5_232201 installed and I've never seen any need to change it.