When I had that issue ...a battery resloved it quickly.
Also recently my friend with a 9700 constantly had an alert appearing on his phone "memory needs to be repaired", when he clicked yes to repair, next message alert "if cluster are found should it saved?"
Anyway suffice to say his 9700 could not repair the card whether or not we chose to save the clusters.
I popped out his SD card and shoved it in my 8520 and just to make sure his phone had no hardware failure. My phone did the same song and dance then I proceeded to hooking up the phone as mass storage device to my pc and scanned the card with avast antivirus....needless to say the card was loaded with malware, spyware and the dreaded shortcut virus. I had the antivirus remove all malicious strains and then had windows check for bad sectors on the card and recover. Then backed up stuff he wanted off the card, then and most importantly FORMATTED THE CARD USING THE BLACKBERRY....never format a card using windows then use straight on the phone let phone arrange memory clusters on the card the way it wants.