VOIP321 gurgles after new mobo, usb audio problem?

Hi, I have a Philips VOIP321 Dualphone (Skype&PSTN) connected to one of my
USB2 ports. Everything worked just swell on my old HP dx5150(MSI mobo,
MS-7050), until I blew this up (don't ask). I have now replaced that mobo
with an ASUS board, A8N32-SLI Deluxe. The OS took this heart transplant
remarkably well, the VOIP321 unfortunately less so. The sound that I hear
gurgles and slurs. This is *not* a Skype issue since (i) my interlocutor can
hear me perfectly fine and (ii) it happens on practically every call while
sound problems were rare on the old mobo. I am running 32bit Win XP Pro SP3.
I am unclear on how the VOIP321 implements Skype but have the suspicion that
it leaves the sound processing to my computer. However, I do not believe
that the RealTec Audio driver of the new mobo is involved, but that it is
rather Microsoft's USB audio driver 5.1.2535.0 (dated 1 July 2001) that is
doing the work (the VOIP321 shows up as a USB audio device under Sound
Devices in the Device Manager). I had a look around Microsoft's KB and found
a reference to a problem with that driver (KB898108) and associated hotfix
dated August 2007. When I tried to install this fix, I am told that my
service pack post dates it and that I therefore do not need it. I don't
quite understand this since my usb audio driver clearly pre-dates this fix.
Could anyone advise on how I might go about fixing my sound issue? To me it
sounds as though some buffer somewhere is overrun and the required
retransmissions slur the whole sound track until is all becomes rather
unintelligable.

Thank you.