I had a Handcent problem too but not this. I found out from them that Handcent does not work right with Antivirus apps on the same system, and there is no need for one. They said they were getting all sorts of different bugs just because of this.

 

Well, I guess just for future reference, I use ChompSMS and have had 0 problems with it. Maybe you'd want to give that a try?

 

Download the sound manager app. It fixed my issues with Handcent not vibrating. There are issues with Handcent and the Incredible, so its not just you. The vibrate doesn't work properly, but somehow works once you download sound manager. There are settings for notifications within sound manager, make sure the vibrate stuff is on.