An issue we ran into once we’d installed Ice Cream Sandwich on the HP Touchpad using CyanogenMod 9 was that we had no USB access. Just an error saying there’s no driver available. This is down to a setting within CyanogenMod and ICS.
To get PC USB access working with the HP TouchPad and ICS you’ll need to select Settings > Storage locate the three-dot menu in the top right of the screen, crafty huh? Or stupid. Tap this and a menu will open with USB computer connection as the only option, tap this. A new screen will appear with two unselected options select the Media device (MTP) option.
If you now plug in your HP TouchPad you will still get a driver issue but the device will appear in your My Computer as a new media device that provides USB access to the root of it.