Comment 18 for bug 1448441

Same here for the following system upgraded to 15.04 from 14.10 yesterday...

System Information
 Manufacturer: Dell Inc.
 Product Name: XPS L421X
 Version: A04
 Serial Number: JG74GS1
 UUID: 4C4C4544-0047-3710-8034-CAC04F475331
 Wake-up Type: Power Switch
 SKU Number: xxx123x#ABA
 Family: 103C_5335KV

This also seems relevant...

Handle 0x0028, DMI type 27, 14 bytes
Cooling Device
    Temperature Probe Handle: 0x0029
    Type: Fan
    Status: OK
    OEM-specific Information: 0x00000000
    Nominal Speed: 0 rpm # while the fan is audibly running!

Handle 0x0029, DMI type 28, 22 bytes
Temperature Probe
    Description: Temperature Probe
    Location: Processor
    Status: OK
    Maximum Value: Unknown
    Minimum Value: Unknown
    Resolution: Unknown
    Tolerance: Unknown
    Accuracy: Unknown
    OEM-specific Information: 0x00000000
    Nominal Value: 2594.0 deg C