question about import data

[Ming Yang <myang@xxxxxxxxxxxxx>]

Hi, all
    I encountered a strange problem right now. I try to import a data set
into ferret by using SET DATA or USE command, but I got an error message
like this:
 **TMAP ERR: non-existent or not on line
             atmmmyl001711.nc

How it happen? BTW, the version of my ferret is 5.70. Thank you in
advance.

Cheers,
Ming