Aspire 1800 : installing XP SP3 makes internet crawl

Acer Aspire Laptop 1800 (Intel) Windows XP Home

connected to ADSL router (Zyxel) via 54 mb. wireless.

Installed release SP3 today and found internet performance dropped to less
than 10% of normal.

I had tried installing the preview version of SP3 two months ago along with
Internet Explorer 8 beta 1 and had the same problem. Removing both of those
restored internet performance.

Just curious if anyone has any information or ideas other than the obvious
which is to un-install SP3.

thanks, Bil