I have not clue about the late txt messages...it could just be a network thing, but I've heard of similar issues with voice calls. Has this happened to you before? It could just be bad coverage resulting in dropped calls.
If callers are truly not hearing any rings and it goes straight to voicemail then I recommend you flash back to stock rom (and radio) and see if problem persists. If it does, there's a hardware problem with your phone. Otherwise here are some things to consider:
1. are you using a 3rd party app like Photocontacts Pro, phonelarm? If so, is it installed to main memory?
2. Are your ringtones on the storage card or main memory?
3. Are you using a 3rd party PUSH service?
4. If none of the previous questions apply to you, perhaps you should check this thread regarding 'delayed ringer response'. Basically with CDMA networks like Sprint, the network fakes out the caller with a "fake" ring or two while trying to find your phone on the network. Here's a fix
http://pdaphonehome.com/forums/ppc-6...cle-index.html