How to remove Mac formatting on compact flash card?

Background:
My wife owns a Janome 9700 embroidery sewing machine that uses 67Mg compact flash cards to access new embroidery designs. The machine formats new cards for Windows and which can be loaded with new designs from a Windows machine. Recently, I downloaded an embroidery design for her on my Mac Powerbook and, reasoning that I could simply load the design on a pre-formatted Compact Flash card via a USB card reader linked to my Powerbook, proceeded to do so. The result was that the card, when placed in the Janome sewing machine,l generated a "FAT error" message and asked if I wanted to reformat. When I agreed to do so, it responded with a read error and refused to format the card., rendering it useless for use with the Janome sewing machine.

Questions:
1. How does the Mac OS 10 modify the formatting of the card so that it is unredable by the Janome? The card is still readable by both my Mac and our HP laptop running Windows 7.
2. Is there anyway to wipe the card so that I can reformat it on the Janome?

Thanks

I think your flash card is corrupted. If the Mac can't erase/format it, try it on Windows. Make it FAT/DOS format.

How does the Mac do that - don't have a clue. I'd be surprised if it happens again.

The card was probably formatted using the GUID partition scheme. That will render it unreadable or at the minimum as two partitions. Always check to see that "MBR" is selected when formatting a SD card or flash drive with your Mac and using FAT-32.

It has certainly been corrupted as far as the Janome sewing machine is concerned, but I can still read the files via a USB cable on both my Mac and our Windows machine, as well as add and delete files. Apparently the MAC OS changes some small bit that the Janome looks at before loading. Could probably reformat using either my Mac or the PC, but would that then allow the Janome to reformat it for its use? May just have to try and see what happens.
Thanks for responding.

I've run into that before when formatting flash drives as FAT-32 using Disk Utility. As I stated above, if the MBR option is not selected Disk Utility will create a small partition on the flash drive in addition to the main one. It really messes up the flash drive for use on anything else except a Mac.

You'll need to reformat that drive on a PC but first you have to remove that small partition which is not easy. Go to this LINK and follow the instructions. You'll need to use a PC to do it.