Lg 50px1d-uc -bottom half of picture has color thin vertical line, top half is fare for about a minute then goes to vertical colored lines, there a thin white hozontal line dividing the top and bottom

SOURCE: I have an LG 44inch

Just check if the lamp is good and don't have any problem and then go for power checkup..it might be because of bad power..

SOURCE: TV runs for a limited time, then goes to standby

Is the fan running ,if the fan has dirt on it clean it off with contact cleaner.Set will stop playing if fan stops.

SOURCE: picture loses all normal color & changes to snowy blues & greens

Not sure what causes it but it can be fixxed by your local repair guy, I just had mine fixxed for under a hundred bucks, he takes the back off and with a tiny screw driver adjust a few screws to near brand new perfect picture.. and it has been good ever since

SOURCE: dead screen

this would be due to a convergence issue either in the color wheel or the ballast. It is probably a balast that will need to be replaced.

SOURCE: I have a LG 50PX1D-UC plasma TV with a black vertical line

You could have a Driver Board that has a loose connection or a Ribbon Cable that has a intermittent connection to the Plasma Panel, or a defective Plasma Panel. Either one could cause the problem and I would recommend only a Qualified Service Person to check it out.
Here is LG's Customer Service Number. 1800-243-0000. They could direct you to a Local Service Facility.
I hope this helps,
Sky Assoc