iGo 8.3.5.23118 Navon is a newer version of igo 8.3. I also have a Mio C320 and that version of igo runs fine with it. There are some igo licenses that requires a SD card inserted on the device. Since you said that you are already using a SD card, I don't think that's the issue. It's also possible that you may have corrupted content file (map, poi, etc). Try re-copying your content from your PC. It's also possible that the SD card is corrupted. You can also try reformatting the SD card or try using another SD card.