IP TV makes Sonos crash

Hi,

Every time I start IP-TV the Sonos stream stops - and vice versa.

The setup in the house is as follows.

Tel.line
-> Thomson ADSL / WLAN AP
-> HP ProCurve Switch (wiring closet)
-> Netgear (pure) WLAN AP (SONOS ZP90 is wired here) AP
-> 3Com Switch (Motorola IP-TV set-top-box is connected here)

In addition to this I have 3 other Sonos components connected wirelessly. I could connect more with wire, if needed.

I'm controlling Sonos with Sonos CR200, iPad, Galaxy TAB, Galaxy S3 and Macbook Air.

Anything I could try to solve the issue?