Problems with Mega 2560

Hi,

I was using the Arduino Mega 2560 to read out temperatures with a NTC 100K Ohm sensor. Everything was working very well, but recently i used an other NTC. An ntcascwe3.
Datasheet: http://www.vishay.com/docs/29065/ntcascw.pdf

When i connected that sensor to pin a1, just like i did with the other NTC it's not working anymore. It seems like he can't read out anymore. If the voltage over the pin gets lower, he doesn't see it. It is just giving the temperature of 130 degrees, even on roomtemp. 130 degrees comes with 2V on a1...

Do I use a wrong sensor? What can be wrong about it? How to fix the arduino board? (Because it isn't working with the other sensor as well.)

Thanks!

How exactly is it wired up?