Arduino mega stop reading DS 18B20 sensors at a higher ambient temperature


A while ago, I asked you to help with the project for my showing temperature on heading system
( arduino mega+ethernet shield, 18 x ds18b20, 5x 7segment display and 2 20 x 4 LCD )

Arduino is located in the housing on the stove with all display.
All project work fine ( 3 months or more ) but problem is, when i burn stove.

Maximum temperature in the housing where it is arduino is 35C , and then the problems begin.

From all DS18B20 sensors I get the value -127.
Arduino work, web server work, DHT22 sensors work.
I try disconect 5V from sensors and reconect and then work again for half hours, then all sensors have -127.
When the housing has a temperature of about 30 or less all work fine.....

What could be wrong? Is this too high ambient temperature for the arduino ?

Thanks for help