Recently I've also been having these issues with my 'new' router (that I got back from RMA a month ago). Specifically, the interfacing and web page loading became slow/inconsistent such that my steam DL speeds for Portal 2 varies from 1.5 mb/sec to 6 mb/sec every dozen of seconds.
As for 1/2 loaded router UI pages, I fixed that by erasing the NVRAM (telnet into router & typed mtd-erase -d nvram) and then reverted to another firmware (Currently using version .220 ~ the .24x and .26x 'for me' are overly sensitive to wireless interference... I've searched this forum for solutions but none worked - anyone that walks pass still will create stutters for online games/videos streams).
My RT N66U Router Experience to date.
- Bought it in June. Everything worked flawlessly up until after the time that they introduced .162 version of the firmware, before then I had constant 4.5~5.5 MB/DL with version .151 which was 'lightening fast'. It had two bugs though which a) UI loader didn't spin properly, and B) Issues with setting up FTP servers. Nevertheless, the speed at that time was still incredible.
- Around August to October, problems started to appear after the .178 versions and newer firmwares (although later on I started to think that it wasn't the firmwares fault). Router finally shorted... (don't even know how but that was what the RMA result had stated after I sent it back for repairs).
- A month a go got back the router (seemed new because it was all wrapped up with protective coverings, but who knows). Worked okay for a week then gradually the internet speed became inconsistent. Have tried putting in Cat7 cables instead of Cat5e cables but to no avail, same with erasing nvram then uploading different firmwares which did nothing as well to help with the spikes. (didn't think it was anything to do with firmware anymore because the DL speed on the .151 version now appeared inconsistent, which wasn't the case originally with my first router).
Basically I'm just lost. I think I'll try to replace my old 4-5 years old Cisco RG59 coaxial cable with a new RG6 cable. If that doesn't help the network spike then I'll probably RMA this Router as well
The only reason I went for an above average router was to try not to waste my family's $100 'discounted' internet plan... not sure if it's even worth it at this point.
I'm still very much open to take in suggestions as my coaxial cable from my service provider will come in later next week.
EDIT: Any new tips given at this point... I would greatly appreciate it.