MobileMeter

A few things come to mind that might cause that:

1. ACPI somehow got turned off in the BIOS, not very likely but something a quick check of your BIOS settings can lay to rest.

2. The temp sensors have failed, which also seems unlikely if you had multiple system monitors, but if it did happen it'd be something you'd want to address sooner rather than later because they are used by most models to decide when to turn the fans on and at what speed.

3. The display listings for those devices have just gotten turned off. If you right click on MobileMeter's window and choose Options, you should see the ACPI Temperature tab. Click on it. If everything is greyed out, see items one and two as possible explanations. If the drop down at the top is clickable and shows a list of devices, you should be able to check the box labeled "Display temperature" and it would add that item back to the list of displayed temps.

If ACPI is on, the sensors are working, and MobMeter's options are set to show all the temperatures listed under ACPI, that's a tricky one. You might want to try running another temp tester, like SpeedFan to see if you get the same readings from it. If neither one detects any temperatures except the hard drive, you might want to consider having the laptop serviced to make sure the sensors haven't failed.