Not well made TV.
Boards: http://www.shopjimmy.com/catalogsearch/result/?q=Protron+PLTV-4250
You need to do indepth troubleshooting, starting at the power supply module first by looking for bad caps with domed tops (notes: bad may look normal).
Please read my guide first before DIY. Shop rate will be $150 and up plus parts, just to tell you what is wrong can be $75 and up.
More likely to have the same problem as the 32" version as shown in my pictures here:
http://s807.photobucket.com/albums/yy352/budm/Protron%20PLTV%203250/

If you are going to DIY and have proper tools, electronics knowledge, and know safety precaution then please read on:

Basic LCD monitor and TV troubleshooting guide:
http://www.fixya.com/support/r5093881-lcd_flat_panel_tv_troubleshooting_guide
http://www.fixya.com/support/r6150077-basic_lcd_monitors_troubleshooting
http://www.fixya.com/support/r7406380-tv_training_manuals
Failed TV and Monitors: http://s807.photobucket.com/albums/yy352/budm
Learn about bad caps: http://en.wikipedia.org/wiki/Capacitor_plague
Parts: www.shopjimmy.com
Capacitors kit: http://lcdalternatives.auctivacommerce.com/Default.aspx he can make you a set of caps.
Or www.digikey.com, just make sure to use caps with low ESR, 105c, high ripple current and long life rating such as PANASONIC FM or FC series.
Please post back what you find.
Please leave rating if it helps.