Don't give up on the reformat. It isn't really a hard thing in _principle_.
It seems some operating systems make it hard. Not sensible, but, they do.
Basically, you have to do 2 things if you're going from scratch corrupt:
1. Create a partition table, partition, partition type.
2. Create a FAT32 filesystem in the partition.
There is a thread on here saying that WINDOWS MAKES THIS HARD with 64GB, but PEOPLE ARE DOING IT.
There is some utility, there is a link that was mentioned on here in the last week or two, even if you're using MS you CAN DO IT.
It isn't a Sansa issue, you shouldn't send the card back. It is probably a "you're using Windows" problem.
(I use Linux, so, I don't have such idiocy as "can't format 64GB to FAT32 easily".
But, that is the part not to give up on, as it is a Windows problem, not a hardware issue.