SB Live 5.1: Lockups when using SPDIF passthrough

Hi!

I'm using a SB Live Player 5.1 card which generally workes
fine under WinXP SP1 with normal speakers.

Now I use a Creative Inspire 5.1 Digital 5500 speaker system
and have a problem:

When I play DVDs and activate SPDIF-passthrough in the
player software, the programs often hang. This happens
especially in the DVD menus or when I use fast forward or
the seek bar. The only way to end them is killing the
process via task manager.

The Problem seems to be independent of the player software.
I tried PowerDVD 5, WinDVD 4.5 and 5.0 for DVDs and Zoom
Player 3.10 for avi/ogm files with ac3 sound.

When I choose the normal 2 speaker playback, everything
works fine.

I already reinstalled the latest SB Live drivers, but
without success.

Thanks in advance for your help!

- Stephan