As jsh1120 stated, it is not only a Handcent issue. I have never had handcent but I still suffer from this issue.
I have noticed the same casual factor as PearlMikeJam. My live wallpapers only revert to non-lwp when I am using my soft keyboard over my home screen. So if I am doing a google search using the Google search bar, or if I am replying or sending a text using a Quick text pop-up.
It will not happen no matter what other apps I use, and I know there have to be more memory intensive apps then my soft keyboard. I have tried to switch soft keyboards, but that has not solved the problem. It also does not happen right away. Often, if I type quick enough, I can get away with using my soft keyboard over my home screen. I have timed the event, and it seems to consistently happen after around 15-20 seconds of typing.
I do not have a Task killer program, and this has happened on my last two phones with android 2.1. Both were Motorola Droids. One had the issue right out of the box. I have tried factory resets with no luck. Seems to be a bug revolving around the soft keyboard, but I am not tech savvy enough to know exactly what the problem is beyond that.