ASIO playback acting up in second user account Options

[Nordfinn]

I don't know if this is a Foobar question, per se. But: I have two identical foobar setups on my XP desktop, one for Administrator account, and one for guest account (gets used by houseguests). ASIO playback (Xonar STX ASIO device) works perfectly in Administrator account, but not in the other. In the other works fine until I have another process going, even the lightest web surfing. Then I get all kinds of juddering. Have tried setting the latency to maximum for the ASIO driver and also setting the buffer way high. Doesn't help, or only minimally. Happens whether or not I have first logged into Administrator account before loading as guest.

Anyone know why this would be?

Playback with non-ASIO driver is fine, in both accounts. I am running Foobar 1.1.13.

Thanks,
N.