same happened to me using old os2007 version. new firmware seems to have solved it.

When doing video convert, i write onto pc and later copy video to n800 that has card. Seems less dangerous. video writing may try to write faster that n800 can take it if you try it in one step. Just a guess....

I sent memory back to manufacturer, Transflash, and thew sent a new one. So think twice before you throw it out.