Sense is resetting with two possible causes -
1. It's run out of ram and bailed out to give your other apps priority.
2. Your internal caches are messed up. Android has a main one, most all of your apps do as well.
You can do a cache cleanup if you're not rooted by performing a factory data reset.
Backup your apps and data using Carbon backup, your texts if you want them using SMS Backup+, and be sure that your contacts and calendars are on the cloud by checking your Gmail from the web on your PC. Good idea to also backup your sd card while you're at it.
Then factory data reset and restore things. You'll have to re-enter your accounts.
If that doesn't cure it, then you either have an app misbehaving in memory, or you have too many apps.
If you have a lot of texts stored, start by just backing up those and then deleting them. If your dialer is slow to respond, that could be the cause of that and your launcher resetting - because everything is tied to everything in Sense.
Hope this helps!
