I'm not sure if this is the same thing you're talking about, but one time I had a tethered jailbreak that I tried to reset and it got to the Apple logo boot screen and seemed to crash. I thought I had no way to boot tethered anymore as I couldn't get into recovery mode because the iPad would try to boot whenever I plugged it in to the computer.
If you hold the power/sleep button and the home button at the same time, it will shut off for a second and then turn back on (it resets). Use that one second to pretend your iPad is off and begin the button pressing then. In other words, hold power and home until it resets, and once the screen goes black, release them and then start holding only the power button (then after x seconds, the home button, etc). I've done this three times with boot loops and it takes some time to get things timed right, but it works.
Also, these may not be exact instructions. I think they are, but I remember playing with it a lot to get it to work. If you have the problem I described though, it will work.