Trouble with Toshiba flat screen

you probably have voltage problems , you might want to check the source, the componenes , such as capacitors and ic

Is the power led on? Is the panel back light on? Tap gently on the screen. if you see whitish on the screen when you do this the panel is on. Press menu button does the menu appear?
if the set is 5 yrs old or older many times capacitors on the power board go bad. They are recognizable by a slight domeing on the top instead of being flat. these are replaceable at component level.
you can check on ebay under the model number for a board. The board is held on with screws and plug in connectors.

I have three places maybe that will be able to help. TigerDirect, Full Compass, and last "Radio Shack"

Did it just start doing this? I don't think the issue is of one related to age. Do you have it placed next to a floor register or some such product that produces heat? Look on the backside of the tv where the vent bars are, and see if they are coated in dust. Have you called the manufacturer to ask about it? Sometime by asking at work or talking to friends you can find the answer, or get one of those :light bulb moments over your head.

Main board fault. Contact any service technician or the authorized service center for Toshiba. If you wish to get some details; check the site linked here. Viewing it in "Mosaic" or "Magazine" will make surf easy. Pull up older posts. Surf the site with patience. Do a search by type in the brand name of your device at its search box and press "Enter".
http://electronicshelponline.blogspot.com/
Service mode entry, adjust and exit procedure to many popular brand TVs are given. Never forget to exit the service mode, after all adjustments have been done.

Check for it at its main power regulator board.

I called Toshiba for this TV model "40RV525R" and they said the pedestal stand for the t.v. to stand on was an m5, product # 75012791, and the length was approx 20-25 mm

Looks like video problem. Contact authorized service center.

Sorry, I donʻt have solution, but I do have this exact same problem, same model of TV! Iʻm wondering if youʻve had it fixed yet and if so, how did you do it?

I've had the same issue! This is caused by the control panel telling the TV what to do - does it change channels on its own, too, or turn off or on on its own?

What you need to do (if you've not already done it) is lock the control panel out, which you can do under the LOCK menu.

What may help is running the factory reset on page 54.