My 8320 is CONSTANTLY FREEZING. I have cleared and basically disabled the error log, I've uninstalled all of the programs I no longer use. I have done more than my fair share of battery pulls in the last two months. I close programs when I'm done using them...I don't know what's happening, but it sucks.
I would have suggested reload of the software too, and make sure you have the most up to dated software version... 4.5.0.138 for verizon phones. you'd have to verify with your carrier.
+1 on the media card. Take it out and see if the BB stops lagging and freezing. If it performs much better, do as MrWheelMan suggested, take your files off the card, reformat in the BB, then move your files back to the card.