Yes, it still does it on single mode G with and without security on. And that's with just my laptop wirelessly connected to it (nothing wired connected either).
I know I'm also having the same problems with my wired connections because the past couple nights, when my laptop would randomly go out (wireless), my Boxee box (wired) would lose connection right along with it. So, yeah, it's both wired and wireless devices going out.
I turned off QoS and traffic shaping was on. I haven't had any connectivity issues yet, but it is REAL slow still. And it was never this slow before say, this morning and I haven't touched a thing. I just did another Speedtest, and over wifi, I'm 0.91 down/0.45 Up, while my wired connection (from the DIR-655) is 18 down/0.48 up (wired directly from the modem is more impressive (33 down/.48 up)). Something is just not right. But since I turned off QoS, I haven't lost connection. That might mean something...or, like I said, it might take a few hours for it to go down again.
Would upgrading to 2.01NA do any good?