i dont know if this will help you guys or not, just wanna share my idea, and sorry about my english cause im not a native speaker
i got 5 pc , 3 wireless and 2 wired, 1 wii and 1 iphone 2 itouch at my home, dir 655 is just like a hell, freeze everyday sometimes dc every 5 mins
so what i did first is upgrade firmware, disable everything except basic wireless stuff, but still no good
in the end, i found that i dont need wireless n at all, although 2 of my pcs support n mode but i felt it useless, so i forced my dir 655 to work in b&g mode, and since i disabled the n mode, my router is just works like a charm
so if you have freezing problem, try disable your n mode, i guess its just the processor in the router which is not strong enough to handle due channel broadcast, so its getting overloaded easily
just give it a shot and post your result, maybe can help more people