Why do I have to re-run WPS PBC every time I re-start?

Hi , I'm using a Planex Draft 2.0 wireless router and after several frustrating weeks got it to work connect to my 3 PCs and the internet. This may be because I live in Japan and had Japanese instructions and the dowenloaded English ones were dodgy at best.
My problem is that I every time I restart my main computer, the usb access point doesn't connect. I log into the router through CAT5 cable and have to re-associate the router with the access point either by PIN or PBC on the WPS setup page. This all works fine until the next time I turn on or off my computer and do it all over again. I notice the PIN for the access point is different every time. Seems like this is the problem but can find no way to make it static. This problem occurs with all 3 access points using several different models made by planex.
I'm assuming this is a process that I should only have to do once in setting up the WPS security. Any help would be great. Planex is pitifully short of help.
I'm running WinXP SP2
Planex MKZ-W04N Draft 2.0 11n router and planex USB access points.

Provide a link to the manual for this Planex gizmo, if there is a manual on the web.

Here's the link to the router.
PCI® Downloads _ We Network Your Entertainment !

and here's the link to one of the USB adapter

PCI® Downloads _ We Network Your Entertainment !

All three of my USB adapters have essentially the same manual and software but both exhibit the same problem. It seems to be a standard WPS set up. This is why I'm not convinced it's just something I've set up wrong.

Thanks for taking a look.