Did you do clean installs with Xp on the 2 computers ? Upgrade the BIOSes ? Does it have its own power source(adapter) ? Did you try connecting it to another usb port ? 2 links to get you started. I have no other ideas, sorry.

 http://support.microsoft.com/default.aspx?scid=%2Fsupport%2Fwindows%2Freadme%2Fwin98SE%2Fw98sehardwaretxt.asp#BelkinUSB

http://groups.google.ca/groups?hl=en&ie=UTF-8&oe=UTF-8&q=xp+belkin+hub+site%3Amicrosoft.com&meta=&sa=N&tab=wg