There are one possibility with two results on this issue.
1. The CF pin bent, so cannot connect to NVS correctly.
If signal pin bent, then if the pin straiten, you can use it again.
If the power pin of CF slot bent and shorted, then it can cause power fail.
Pls check if the SD is OK or USB connection to computer is OK.
If the USBconnection to computer is OK, then it means no problem on power block.
You need to use light to check if the CF pin bent or no.
Answer by Chris2012-09-25
Check to see if CF card contacts pin are okay, as suggested above.
If this errors are not related to pin bent, then Upgrade your NVS1501 Firmware to the latest v1.52 or 1.53.
Hope this information helps.
Answer by isupplies2012-11-02
We were brought this unit. In fact the error was corrected by updating the firmware to the current level! After doing this, the card copied fine without a PEX error