Okay, a quick reformat and the 8GB card in the internal slot this time... If I write the files to the SD card via a USB card reader on a Windows XP machine, the N800 appears to be able to read them just fine. If I transfer files from the other SD card (1GB) or internal memory to the SDHC card all goes fine. If I try to download maps or podcasts from the internet on the N800 and write them to the SDHC it goes all wrong. It appears that the write process gets all confused and trashes the file allocation table (?) as a quick format sees the card back up and running. Anyone having the same behaviour?