I have a Sony KDL-52XBR6. It has horizonal lines across the top of the screen. They appear to pulsate. The horizonal lines appear in groups, so that if, let's say, the screen was divided into columns, you might see two horizontal lines, one above the other, in one column, and then moving to the right to the next column there would be 8-9 horizontal lines, in the next column two horizontal lines again, and so forth. Is this a software problem or is the panel defective. Thanks

Usually it is t-con bad. You can find it here:
1-857-237-12 LJ94-02383 Sony KDL52XBR6 T-Con module

link:http://www.ebay.com/itm/170994317153?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649

Based on the information you've provided, I suggest that you update the TV with the latest System Software and check the operation. I've provided a link with the information to download System Software Update:

http://esupport.sony.com/US/perl/news-item.pl?news_id=273&mdl=KDL52XBR6

If the issue is unresolved, please follow the additional steps given below to troubleshoot the issue:

1. Make sure that you have connected the source to the Television properly and securely.

2. Unplug the power cord of the unit from the wall outlet for few minutes, then connect it to a different wall outlet and check the operation.

3. Connect the video source to a different input on the Television and check the operation.

4. Connect a different video source to the Television and check the operation.

5. Replace the connecting cable and check the operation.

6. Reset the TV to factory settings. To reset your TV to factory settings, turn the TV ON. Then, while pressing the UP ARROW or RESET button on the remote control, press the POWER button on the TV. The TV will turn itself OFF then back ON.