Looks like no 10.5.2 for me then,
I tried just downgrading the router to only use 802.11g but it became so slow when using skype 🙁
I wanted bug fixes, I just like living on the bleeding-edge
Perhaps contact your Dlink support for help? Just outline to them that there might be some problems with the 635, since using a DIR-655 works well in n mode.
Pity I have to return the 655 today. 🙁 I'll contact Dlink on my end to see what happens.