Yesterday I wanted to flash a rom via recovery but the flashing got stuck at "opening update package" and then CWM said: error opening rom.zip (bad).
So I did a quick search in the web and I've read that my sd card should be formatted in fat32. My sd card was formatted in exfat and it was partitioned so that could have been the problem. So I formatted it in fat32 (only 1 partition) and everything worked again.
What was the problem? Exfat filesystem or partitioned SD card?