Okay, so I was trying to flash my phone back to stock OS (Windows Phone 6.5) from Android 2.3.3 meguesses, because of too many stability problems I had (tbh Android is cool, but I'd rather have stability then cool features).
So, I downloaded the correct files, copied them over, but my phone refused to reflash. I didn't know what was going on.
I switched to Windows, to try it there, as many people flashing the same phone use Windows just for the sake of it. At least I guessed.
In Windows, everything was fine, and now my phone is happily reflashing (it's at the OS part). Reformatted the SD card I used to FAT32, which I also did in Mac OS X.
What is different between Windows and Mac OS X when it comes to SD cards?