#1, you didn't have the camera system and the mixer clock sync'd. Just because they are the same sample rate, doesn't mean they are in sync.
#2, You stated that you had a power surge. Clearly something went wrong after that and unfortunately there isn't much to explain what happened.
That being said, it sounds like, to me, that your first audio wasn't actually in 48 kHz, but recorded to 44.1 kHz, which will sound 'sped up' when played back at 48 kHz.
There is software out there that can repair audio header files, when the audio was encoded in one rate, but tagged for another, causing software to playback to sound weird. WaveAgent is one such program, I believe.
That's your best bet, is to see if you can recover the files by altering the header data for correct sample rate playback.
If I were you, I would start recording via USB to computer as well as SD. Use either as a back up / redundant recording system.