Andyrod,

Hopefully, you are at firmware 2.09 on the Spider Jam.

In an effort to reproduce the problem, I attempted to save one of my own recordings by hitting 'SAVE', then selecting 'SAVE REC MIX AS WAV TO CARD'. I also received an 'SD-CARD WRITE ERROR' message. Strange.

So, I hit 'SAVE', then selected 'FORMAT CARD'. The Jam formatted the card in seconds and I gave it another shot. It worked that time.

If multiple cards are giving you the same problem after following the steps above, there must be a hardware issue with your amp and needs to go to an authorized service center:

http://line6.com/service_centers/

Regards,

Line6Hugo

Not sure if this is of help to you but I made so many mistakes when I first began recording songs with my amp that I finally developed a work flow that minimized my frustrations.
I haven't tried recording and then saving directly to the SD card.  When I was using the amp to record tracks in the past, I would always save the recordings to the amp until I was satisfied with the song (and had it saved to the amp in it's final or close to final version).  Then I would move it to the card and then I would save it as a wav file so I could transfer it to my computer.    I am sure there are shorter cuts but that is what worked for me.