I am suffering the same issues sporadically on my Sensation.
The Sense UI is crashing, but the notification bar, etc. are all fine.
Think I may have to look into replacing the launcher as folk have recommended.
If you're using a task killer then remove it and your issues with Sense crashing should solve itself
) and uninstalled it
)
I really2 fedup. Until i think do i need to reset my phone to original factory? i don't want to lose all downloaded application and other things in my HTC sense.