I switched from a Pearl to a 8310 last week, and thought I would give DM 4.3 a try - what a mistake!! Granted, the UI is nicer, but the functionality was junk! I also had trouble with Media Manger loading, Outlook synch, Bluetooth connectivity, etc. I messed with it for a day or two, and went back to DM 4.2-SP2 (
https://www.blackberry.com/Downloads/browseSoftware.do ). In the course of about an hour (most of that was installation time) I was up and running perfectly! I use it for all functions with 2 totally different phones / OS (my Curve and wifes Pearl) on one laptop, and it always performs very well.