The host machine may be NTFS which allows some name that isn't allowed on the SANDISK drive.
Too bad you didn't share the gritty detail of the names.
It's also possible to overflow the ROOT DIRECTORY of a filesystem. How many files and directories are in the ROOT?
I have a scan disk cruzer flash drive, and sometimes I can save to it and sometimes not. Sometimes I can move from my hard drive to it and sometimes not.
I generally get the message that the directory of file cannot be created. I've got room on the disk, any idea what's up?