Let me explain something to you.
Every router treats DHCP slightly differently.
I've seen some by some off-brand names and by another enterprise deployed one whose name I can't remember who don't seem to respect IP reservations the way I would expect them to.
Similarly, I've seen some older Netgears with other weirdnesses with VoIP devices, which is a type of streaming (audio).
Apple cannot test the apple tv with every configuration, and neither can Netflix.
What I would encourage you to do if you want this fixed is to post your router make/model, your ISP, does it only happen in HD, because you know that sometimes rarely happens to me too.
But most of the time, my Netflix works great.
In terms of reserving IP addresses, actually the previous poster was slightly wrong in his instructions.
You reserve IP addresses in the DHCP range, so if it's 50-100, you reserve the IP that the apple tv currently has when it's functioning. you don't specify it on the device itself, unless you're specifying outside the range, which is not good practice.
In general, I would say replace the router as a first step... as someone mentioned, you can test this by going over to someone else's house.
I don't think this is a bug, but I could be wrong. It may also not be in the software, but in the CDNs. Keep in mind the CDNs change when you change DNS. You may want to ask your ISP if they have alternative DNSes if the primary ones don't work for you, but in general, you may experience worse performance using DNSes that aren't local to you.
There's a way to find out which DNSes are best. You can use any DNS, it's an open protocol.