MicroSD cards stopped working after OSX 10.9 installation, why?
Are they NTFS formatted? I am having trouble with flash drives that are NTFS formatted. I use the free NTFS-3G software and am guessing that's the issue. One post here seems to echo that sentiment:
CNET NTFS-3G user review
Also, found these Apple support posts where people indicate their problem is solved with NTFS-3G and Mavericks
https://discussions.apple.com/message/17356645#17356645
http://osxfuse.github.io/
I was having a similar issue - this helped me: http://www.youtube.com/watch?v=nbc0l-t3f1Q