It's a fact that the majority of users is unable to configure a network when the environment requires a bit more than "working out of the box". I might be putting it bluntly, but there's no qualification attached to this simply because you don't have to be an engineer to drive a car.
Asking for a solution because I'm an IT pro... even when a lot of info is given, (network) environment factors cannot be taken into account of seen. It's like consulting a doctor by phone; it's quite limited.
Why don't you show your configuration (or environment) in which your router works flawlessly?
(1) Windows OS
-. Which setting do I need to adjust in OS (XP or Vista)?
-. Network card? Since I have several computers - thus, different network cards -
which have all the same problem, I don't expect any special tune for the cards.
But if you have any, please elaborate it.
-. Firewall doesn't matter, I think. (the problem still happens even though it was turned off)
but, if you still want to recommend something, please elaborate it.
(2) DIR-655
-. please share your setting.
Any special setting you did?
Setting USB network is relatively simple.
But if you have any, please share your setting info.
Please don't just say, "Oh, it's hard to explain, blah, blah, blah",
if you really think that the issue is not on the DIR-655 router/software
but on the lack of users' IT knowledge.
If you're not able to share or to give the info which can fix the problem,
please please never ever post like that.
I have already read too many posts
-- no help, but just irritate those who want a router working as it is advertised.