XFCE 126.96.36.199 (Xfce 4.4 BETA1) has been suddenly relocating app windows all by itself on an x86 running Zenwalk 2.6 (Slackware). I installed a month or so ago, and it seems to have started maybe a week or two ago and maybe gotten worse in the last few days. One moment a window will be in one spot, then it spontaneously moves to another. I thought for a while that one window (Thunderbird) had disappeared, but maybe it just got moved off the screen. The moves may be triggered by something I do, but I'm not sure. The last one occured when I switched between desktops.
Not seeing that here. Please update to xfwm4 rev 22776 or later and report.
(please note that 188.8.131.52 is beta 2, not beta 1, so I'm not sure about the exact version you use)