thanks Huskur for your help.
and just for reference, if the other two posters would have taken the time to actually read the thread, they would have seen that I was NOT referring to getting 1 notification from Handcent and 1 from the native Messaging app. I've done plenty of searches through the forum and that is the only problem I see people having. As mine seemed unique from the 20+ posts that I've found, I posted.
I agree 100%. The last time I chastised someone for doing this, though, I got a slap on the wrist from one of the mods because I was being "mean". So make sure you tone down the sarcasm when you tell someone to read the thread before posting or some of the mods might be around to yell at you for not being "nice". Ironically the first two posters basically called you a noob for not searching but couldn't even read the first post in its entirety.
Anyhow, I had the same exact issue this past week. I removed all check boxes and whatnot from the stock messaging app and I was getting two of each message. No idea what suddenly caused it to happen more and more often, but I uninstalled Handcent and have been using only the stock messaging app lately...no issues since then.