I`m getting a black rectangular box in the middle of my LG LCD TV 42" bought about a year ago. This box doesnot disappear with changing channels. Appreciate your help in this matter

Sounds like you have a cluster of dead pixels.

If you're still within warranty, contact LG directly. If you purchased extended warranty, then contact the store you purchased it from.

This is generally not economically feasible to replace, but it is covered under warranty. If you're out of warranty, then you're most likely going to be shopping for a new TV.

Good luck.