wireless lan performance

I have a wireless router (D-Link DI624) at home, with the following setup: one pc ("A") is directly connected to it and the other pc ("B") is wirelessly connected. Now when I'm using "B" and I copy/view files from "A" I get a decent 108MBs transfer rate for the most part, every 40-60 seconds there is a stall, as though the connection is lost, and everything grinds to a halt for about 30-60 seconds, before the copy/playback can continue. This doesn't happen when I copy/view files the other way round.. Has anyone round into this kind of problem before? Perhaps losing signal? But why so regularly? When I run Process Explorer to monitor the activity I noticed a spike in DPC ('Deferred Procedure Calls') when the network stall happens.. Perhaps an irq conflict of some sort, since the netcard has to share with the audio (but windows allows irq sharing)..

Anyways, just checking if any of you guys may have an idea,
thanks!

Kris