Tassimo 1000UC model descaling light is on but won't run descaling process. I've prepared the descaling solution, put in the service T disc and then pressed the center button for at least 3 seconds. Rather than running the descaling cycle, the low water indicator button starts flashing even though there is water in the tank.

SOURCE: Tassimo Goes Right From Auto to Standby

I called Tassimo customer service and they helped me solve the problem. The sensors need to be reset
1) unplug machine
2) Before turning on, push and hold the START button
3) Release the START button after the machine is on
4) Insert T-disc and close lid
5) when it goes to AUTO , press START

this fixed my problem

SOURCE: Braun Tassimo Coffee maker quit working

Hmm if not in covered try

http://rapidshare.com/files/238159116/Braun_Tassimo_3107_Disassembly.pdf.html?killcode=397312781122638452

SOURCE: bosch tassimo

Solution: Just refill the water tank with water (no descaling solution) all the way to the "Max Line". Then run the full descaling program again --takes approx. 20 minutes. After the program runs completely you will get the yellow "standby" light on and the red "descaling" light will be off.

Next time you descale, be sure and fill your water tank to the "Max Line" before running the descaling program.
Hint: An incomplete cycle (not full tank) is what makes the red light stay on. In other words, it's staying red to tell you to run a full cycle (beginning with the water tank filled to the "Max Line"). Hope this tip is helpful!

SOURCE: descaling your tassimo machine

My Bosch manual is very specific: DO NOT USE VINEGAR! They recommend you use any commercial coffee machine descaler.
CLR recommends itself for the job and the Jellmar website has instructions.

SOURCE: red de scaling light won't shut off

Removing the red descaling light is simple.
1. Fill reservoir with half vinegar and half water (no need for the special descaling product from Tassimo).
2. Turn on machine.
3. Insert yellow cleaning disc found in back of machine.
4. This is where most people have the their problem...You must hold the start button for 3 to 5 seconds for the descaling program to start. Both green and red light will flash.
5. Once started, use a large cup to catch the output of water.
6. The machine will cycle through the descaling program in about 30 to 45 minutes. Be paitent!!!
7. Once completed, run many cups of plain water through the system to remove the vinegar taste.
8. Red light problem is solved.

Hope this works for you.