No Heat! Blower works fine - please help

[euro96]

Hi Everyone,
*
On my 2004 X5 4.4, I suddenly have no heat.* The blower works fine, as do all buttons on the climate control (and AC works).* I can have the temp at 90 deg F, and the center vent on heat as well, but NO hot air will come out.
*
What are the first items to check?
-Fuses?
-Heater Valves?
-Heater core?
*
Also, I just had the dealer last week replace the water pump, T-stat, and temp sensor.....could this have anything to do with the heat issue?
*
Thanks for your help!