I love my TC4400 Tablet.
It's a solid machine with only one design nuisance: the volume keys are inaccessible when in Tablet mode.
Yesterday, I noticed something strange: the Tablet would shut down if I was away from my desk and the screen would flicker as it does when it's running on battery power.
Upon closer inspection, I noticed that the power cord was flakey. Look at it the wrong way and the power to the AC adapter would get cut. Manuever it for five minutes and maybe you'd get power back.
I managed to find another power cord to plug into the AC adapter and the problem is better, but not completely resolved.
When I called HP support, I was shocked to get a human being so quickly. I was also suprised when the support agent told me that a "special" department handles Tablet PCs.
Fortunately, I didn't have to wait too long to get the other agent, but I find it odd that HP treats Tablets differently.