My Dell pc hangs while transferring data to/from the Time Capsule

Question

Hi,
I have a really weird problem.
I bought the TC yesterday and I set it up in "bridge mode". So it is connected to my ADSL modem/router via ethernet cable (plugged into the WAN port on the TC) and it creates a wireless network.
My ADSL modem/router is a Zyxel and it's also a wireless router.
My old network setup was wireless-only: the zyxel modem/router was providing access for my Dell PC and my PowerBook.
Now the modem/router is only working as a modem and the TC is providing wireless access for both computers.
Now. Yesterday I was testing the whole thing and I was copying files from the mac to the TC and viceversa. No problem, everything smooth and fast.
Then I tried to copy a file from the pc to the TC and... BOOOM. The pc HANGS big time as it never did before! Not even the mouse is responding, I just have to restart it. Before copying, everything works fine: internet is ok, I can see the TC disk, I can access it etc... everything looks ok. But after few seconds/minutes into the copying, KABOOM.
My PC is a DELL OPTIPLEX GX620, almost three years old. I updated BIOS, chipset driver and the Zyxel wireless adapter's driver.
Nothing. Exactly the same.
My suspect is the Zyxel wireless adapter that is using the "g" standard. In my old network setup all the devices were using the "g" standard. Now the TC is using the "n" standard and, even if it downgrades automatically to "g" to be compatible, it might be that the Zyxel adapter is not handling it very well and it hangs making the whole PC hang as well.
Specs:
PC: Dell OPTIPLEX GX620 with Windows XP (up to date)
Using a Zyxel G-202 wireless adapter USB (connected to the USB 2.0 back port)
Mac: PowerBook 15" almost 4 years old with Tiger (up to date)
TC: Brand new with firmware 7.3.2
Modem/Router: Zyxel with 4 ethernet ports and wireless (can't remember the model)
Unfortunately I can't access the modem/router configuration.
Any idea? Should I try with a different wireless adapter for the PC? Or am I missing something?
Thanks,
Marco

Answer 1

Sorry for my poor english.
What I meant is that my two computers are not connected to the modem/router wireless network anymore and there's nothing else connected to it, except for the TC itself. So the modem/router is, of course, still a router, but it's only used as a modem.
Do you mean I should set the TC as a normal client on the modem/router wireless network? But if I do so, it will work for sure because my PC will then join the modem/router wireless network (and not the TC's anymore) as it always did.
Or maybe you meant something else?