I'm from the Hero forum, but dropped by to see if Moment users were having this issue as well.
I too have issues intermittantly receiving text messages. This week, both Monday and Tuesday I did not receive any until I finally figured it out. This is about the 4th time this same thing has happened to me in the past 4 months. Usually a hard reset or battery pull will do the trick. Yesterday that did not work for me and I instead updated my profile and PRL. Settings>About Phone>System Updates
It seems that many other Sprint Hero users are experiencing this and there is no fix in place, nor is Sprint or HTC giving any info on whether 2.1 will correct this issue. If you get any answers... please post them! I was going to trade my Hero for a Moment, but it seems like this same issue is affecting you guys too.