moocher - I have the same issue with my DIR-655. In fact i went so far to get DLINK to RMA mine, only to have the EXACT same issue with the replacement. The odds of this being faulty hardware twice seems low, but I suppose not out of the question. I am also running 1.21 and have flashed, reflashed and reset to factory defaults until my fingers were raw with out stopping restarts.
thecreator - thanks for the suggestion I am now experimenting with changing the channels. I suppose the best thing to do is start at channel 1 and start working my way up to 11 until the wireless restarts stop?
lotacus - what specific settings are you referring to? Transmission Rate or Channel Width?
Thanks again, I will be sure to post back if any of these stop my restarts.