I had a similar problem when I was running a transient simulation of a pipe. When I set the initial temperature of the pipe the interior of the pipe was very cold (like 100K). The way I solved it was to create a steady state thermal simulation with a temperature load on all faces and set to the initial temperature I wanted. This generated a constant temperature throughout the part. Then in the transient simulation I checked "Initial temperatures from thermal study" in the properties window (right below where you select Transient). Then I selected my steady state study and removed the initial temperatures from the temperature loads.
Hope this helps.
Have you applied the initial temperature to the entire body rather than just the outside faces? Any elements without an initial temperature applied will take absolute zero, so this may be causing the problem. In the temperature dialogue you can select the body rather than the faces;
This should mean all the elements in the model start from 273 Kelvin.
thanks a lot for all! it's works but i solved it when had selected the body in the properties window (left below where you select Transient), because i couldn't select it in the temperature dialogue before (don't know why, i mean the body isn't added in the temperature dialogue)!