V 01.02.31A
This is the error I'm getting too. I wouldn't be surprised if this is the error most people in this thread are complaining about.
RockBox says Sansa Fuze V1 firmware V 01.02.31 is supported, but then errors our with the above error.
The problem is, the "other" sources of the Sansa firmware don't seem to have been updated yet to include .31A
You must download (direct from Sansa) the latest firmware from
http://forums.sandisk.com/t5/Fuze/Sansa-Fuze-Firmware-Update-01-02-31-amp-02-03-33/td-p/139175 (and yes I know the zip says it's verion .31 but it is really is .31A). Unzip this file (fuzea.bin) and remember where you put it.
Then during the installation, when Rockbox Utility asks you for the firmware, you simply point it to the unzipped "fuzea.bin" file (which download directly from Sansa above) and VOILA! Rockbox will support
Sansa Fuze V1 firmware V 01.02.31A!!!
Hope this helps.
~ FredPC