Err: MINTEMP Geeetech RAMPS

I'm just learning about 3D printers. My friend has been using his for about 2 years now. I'm trying to build my own. It's a RepRap Mendel I2 I've modified to print 200mm tall. I've got everything built already. The trouble I'm having is with the electronics. My friend uses a Sanguinololu board with Sprinter firmware (He bought his kit through RepRapPro with Melzi electronics and fried the Melzi board). We've already tested everything on my Mendel. Everything works. I've ordered the Iduino/RAMPS 1.4 board with Reprap Discount Smart Controller through Geeetech on eBay (RAMPS [www.ebay.com] LCD [www.ebay.com]). (It was less expensive than Sanguinololu and I wanted dual extruders.) Since our version of Sprinter doesn't have dual extrusion capabilities or LCD support, I'm using Marlin. (I downloaded the latest from github [github.com]) We both don't know much about Marlin.

Now for the trouble: We've followed all the instructions to the letter. We can get all the motors working, end stops working, LCD display working, etc... My trouble is with the thermistor. I've got 100k thermistors. (My friend bought a 100 pack a long time ago.) Using selection 1 that he uses in Sprinter I get a MINTEMP error. My LCD displays 0/0 for all thermistors installed. We've tried using his extruder and heat bed plugged into my board and same results (My extruders and heat bed work on his board). To test the connections I used a jumper on the thermistor pins T0, T1, T2. My readings for each reads well over 300c (I think it was about 356c). That gave me a MAXTEMP error. Next I tried every thermistor table in Marlin. The results at room temp. were:

1. = 0
3. = -19
4. = -34
5. = -34
6-10. = 0
11. = -26
12. = -39
51. = -4
55. = 0

I changed it back to 1 and set minTemp from 5 to -1. This allowed me to start without the MINTEMP error but my temp still read 0/0. I was able to heat the hot end to 230c (LCD and Pronterface readings) and was able to run some filament through the hot end. Next I tried PID tuning. Those results were:

Kp Ki Kd
19.47 1.71 56.47
20.00 1.77 56.47
21.02 1.89 58.36
21.75 2.01 58.76
19.25 1.63 56.76
19.31 1.66 56.01

Saved it using M500. I restarted RAMPS. Same result at room temp 0/0. I went back into Marling and manually changed the PID setting default to 19.31, 1.66, 56.01 and changed mintemp back to 5c. Restarted everything and received the Err: MINTEMP again. Changed mintemp in Marlin back to -1. LCD displays MENDEL READY but temp is still 0/0 and I can heat everything just like before.

Other settings I've tried:

Different ramps board settings- Board_RAMPS_13_EFB, EEB, EFF, and EEF. Each one at a time respectfully. Different variations of things plugged into the board at one time. Only LCD, only usb to computer, reset button on board.

We've soldered up several thermistors and tried each one. They all read temperature but I'm still getting 0c at room temp on my board.

If it helps, I'm using a S-360-12 power supply. Using a volt meter I've adjusted the trim pot to exactly 12.00v. I am connected to the 2 different power inputs using 2 different cables on 2 different +- sets of posts. Readings on both sets of wires and on board are 12v. So I'm getting the right power to the board. With the power off and on usb power, my LCD can power on and display properly.

I've already contacted customer support through eBay and it's about as useful as calling DirecTV. All I get are standard teleprompter responses. Maybe about a day apart. My last message said it is now the weekend and they will have to discuss this with a colleague.

I know everything is working. It has to be a firmware issue.

I'm thinking that I might need a different version of Marlin or perhaps whatever firmware Geeetech might be able to provide. But it will be some time before I get any useful help from them.
Does anyone have a working firmware compiled for my setup? It doesn't have to be Marlin. I just want something that works.

This may seem a bit obvious, but have you checked the thermistors with a multimeter to make sure they are 100K and not 10K?

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