Damion,
I get the same fornicating errors on large transfers from a. USB thumb device; I have tweaked the Poseidon settings to no avail. I think the Fat95 file system has issues with thumb drives on large transfers. Small chunks go fine; DOS copying does better than WB, and so on. Of I format the thumb in an FFS or so and use it like an Amiga drive, then I get better transfers before errors. What I do not understand is how CF cards (at least everyone I've tried) work so dern well in FAT mode, Amiga modes and over SCSI to card reader, USB to card reader and IDE connections. I get errors on large transfers on the USB bus, but only rarely on DOS shell copies.
When I use an external USB HDD I never see any problems.
"There are more things in heaven and earth, Horatio,
Than are dreamt of in your philosophy. "