Here's a copy of an email from me to SONY Support, if anyone else has the same issue or thoughts......
When I bought my KDL-24EX320 and installed it the TV connected to my Netgear N300 router perfectly. It is located approx 5 meters away and has clear line of sight. Signal Strength is maximum. Internet services such as Lovefilm work perfectly and can stream an entire film without problems. I store many programs on our NAS that uses Twonkey. When the TV was new it performed an update almost immediately and everything worked perfectly. My Mpeg2 shows streamed perfectly and I was VERY pleased. My problems started when my TV download the last firmware "PRIOR" to the current version. My shows streamed perectly however the volume would go up and down on it's own every 10 seconds or so. I refrained from contacting you as it only started after the update and I assumed it would be fixed in the next Firmware. The TV is now running the latest PKG4.002EUA firmware. It resolved the sound volume issue BUT introduce a new problem which has rendered the streaming functionality of the TV unwatchable. From the very second that PKG4.002EUA was installed, my TV simply refuses to stream the Mpeg2 content from my NAS correctly. It works for no more than 2 minutes before freezing, then restarting with the sound way out, freezes some more and then the picture runs super fast to catch up and then freezes sometimes for several minutes! HOWEVER, Internet streamed services like LoveFilm are unaffected. Every other WiFi device in the house can stream the Mpeg2 files still without incident even in the road or end of the garden! NAS is working perfectly, signal is 100% and all the problems started right after installation meaning it must be the Firmware.
