Do you have the current boot code version 1.0.0.12 PC5500_boot-10012.rfb Also there is another version of the firmware released January of 2012 – 4.0.1.12 PC55--=40112.ros The release notes do not specify anything directly about resolving CPU utilization, but it will not hurt to get the new firmare installed and see how the switch responds. Firmware download: www.dell.com/.../DriverDetails
when i was doing the general maintenance checking on PC 5548 switches, one of them was reported as CPU high. but when i was trying to execute command of "show processes cpu" command under exec mode: 1. the system response: "% Unrecognized command" 2. SW version is: 
about the CPU high of PC5548 and command "show processes cpu"