First, make sure you are running the latest version of the LabQuest software. Versions 1.1.1 and newer include updates specifically to fix problems with LabQuests freezing. To update your LabQuest, see
2.If the Home menu comes up, try opening one of the other programs on LabQuest such as the stopwatch. Verify that the program works, then close it by tapping the X in the upper-right corner of the screen. If at this point LabQuest App does not redraw the screen correctly, use the Control Panel to reboot the LabQuest.
3.If the LabQuest gets stuck on the "System is rebooting" screen, you will need to perform a hard reset using the small reset button on the back of the unit. For detail on how to do this, see: TIL 1777: How do I reboot or reset a LabQuest?
Any unit that has this problem should be marked in some way (such as recording the serial number or placing a sticky note on the back of the unit). It is possible that there is a software problem with the unit that causes it to get stuck in reboot. If the unit continues to have problems, contact Vernier.