I was bit late to realize this, but after the recent WP upgrade to 2.1 there has been few hiccups with the UTW plugin (specifically release 3.141592 , that I use). The UTW tags would just vanish whenever a new comment was being posted or when you try to edit the post. Fortunately, there is a cool fix available till a new release of UTW comes out.

Update: It seems the problem is also with Bunny tags, a plugin that my Hindi blog uses. The fix could be found here.