Yes, the green "DVR has detected an error" message does mean your box has failed and will need replacing.
Calling into faults is the quickest way to report this - once you've chosen the options for "I have a fault with my TV service", don't press any further buttons and wait for an agent. If you have any more issues with calling through, do post back with details and VIP users may be able to expedite a response for you.
Otherwise a VM response on here is likely to take a couple of days - hence calling being quicker.
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