My wife and both have a droid x and both use handcent sms. For some reason every time she sends me an Mms the picture comes through in Black and white. Never happened before.
Clear cache/data in the app itself
Another possible scenario is to do the same in your Gallery app
Another possible scenario is to fully un-install Handcent and fully re-install it
All I can think of for now because I am trying to remember the last time I used Handcent....