It's not a generic issue and only occurs since firmware 1.21 or so, so they're kinda telling the truth. And let's face it: what would you expect for $100 device... There's bugs in every software. To be honest, being on the forum dealing with user issues quite a while now (have a look at my stats, 19 positive customers and 6 idiots

), people very often start looking for the error in the wrong location or just leave out essential info. The forum is a much better place to get some help, so you came to the right place.
Using OpenDNS has no side effects or negative impact. It is usually recommended tu use these since ISP DNS servers have a tendency to be slow. And the OpenDNS ones are stable and fast.