You cand fix it by reflashing it with the latest firmware.
To do this you need a usb thumb/flash drive.
Download sp36709.exe from Hps's website to a PC. This is the latest OS.
Run it on the PC and use it to format and load the flash.
Plug the flash into on of the USB ports on the 5135. Turn it on.
If it boots the flash drive you will see the activity light on the flash blinking.
Follow the instructions to reset/update the machine.
I've noticed that the 5135 often doesn't access the flash drive on cold boots.
If you can actually get to the shutdown button when the machine is up, use it to reboot.
If not, try different usb ports and quickly turning the machine on/off until it boots form the flash.
Good luck,
Peter
PS Has anybody gotten one of these thin clients to open multiple sessions and switch between them?