Definitely update to 4.5 but don't wipe your device. Search for Reed McLay's guide to free up file free memory. That what I did and ice never seen my BB run better. If post the link but I'm on my BB. Good luck!
Posted from my CrackBerry at wapforums.crackberry.com
Be sure you exit apps that you're not using. Run the Memory cleaner (options>>security>>memory cleaning). Clean out your inbox(es). Quickpull is a great app that simulates a battery pull. It's a small app, and there's a free verson. I used it every other day on my Pearl and it helped.
I do all of those things, and read the how-to on freeing up memory...I have plenty of memory, a big memory card, and my phone still keeps erasing call logs and texts, once a week or more! This is getting ridiculous!!!
Well, BB has a built in Memory Clean, to check this do:
1. Open up your "Options"
2. Choose "security options"
3. Choose "Memory Cleaning"
--If memory cleaning is set to "enabled", then this is what may be causing your problem. To change it, just click on the word "enabled" and change it to "disabled", exit and save, and you should be good to go. Good luck!
Posted from my CrackBerry at wapforums.crackberry.com