Webcam switches off after call-start

hi

server:

OpenFire v3.6.4 with red5-Plugin v0.1.02 (runs at the Ubuntu-Client)

clients:

Side A SparkWeb @ Ubuntu Jaunty (32 Bit Server-Kernel) + Firefox v3.0.12 + Adobe Flash-Plugin v10.0.22.87

Side B SparkWeb @ Xp Pro SP3 (32 Bit) + Firefox v3.0.12 + Shockwave Flash-Plugin v10.0 r22

problem:

i initiate a video-call on Side A or B (that’s equal) and i get a dialog for asking to accept the connection on the other side. after accept it the call starts and i see the webcam-pictures of Side B, but on Side A (Linux-Client) the cam switched off and so i don’t get a video. i know, the webcam is working with skype…

does anybody know this problem?