2 USB drives at the same time

Hi,
I am not getting both USB flash drives mounted and indexed.

/etc/mtab shows that both drives are mounted to /mnt/USB …

[size=85](/dev/sdc1 /mnt/USB vfat rw,relatime,gid=100,fmask=0002,dmask=0002,allow_utime=0020,codepage=437,iocharset=ascii,shortname=mixed,utf8,errors=remount-ro 0 0
&
/dev/sda1 /mnt/USB vfat rw,relatime,gid=100,fmask=0002,dmask=0002,allow_utime=0020,codepage=437,iocharset=ascii,shortname=mixed,utf8,errors=remount-ro 0 0)

[/size]
…but when I do a ls -l /mnt/USB I do see only the content of one drive, and after updating MPD database it also shows only songs of one drive.

I have tried several things that I read like booting with one, then plugging in the second, or booting with both, and so on, nothing helped.

Any ideas?