m2ts video and other HD video is not running without breaks

I'm using win 7 32 bit and a sony LCD TV. (Sony Bravia KDL-40EX725BAEP 102 cm)
On the Sony TV the videos are running stuttering. dLAN is the connection not WLAN

the thing is: it was running very good a few moths ago and I have nothing changed on TV or LAN . I tried older versions and newest.

dLan1: 166 Mbit/s and
dLan2: 120 Mbit/sek

between dLan circle1 and 2 is the fritzbox router

[atc98092]

That is certainly enough bandwidth for HD video. The highest bitrate I've ever seen from an M2TS file was about 55Mbps. I've also encountered issues with Sony BD players. Same symptom: no changes in firmware or other issues, but suddenly movies that played fine started freezing. Personally, I believe Sony did something in one of their "Internet Video" updates. That's the only thing that my boxes updated in the last 6 months. No idea if that has any truth to it though.