Error 60, Invalid external unit identifier - HELP

Can anyone explain this error for me? The FTN95 manual give no information on the cause of this error.

Does anyone know of any link where these errors are explained?

Please help, Jonathan

The only way that I can reproduce this error is to make the unit number negative. It is recommended that unit numbers start at 7 to avoid standard units (usually 1,2,5 and 6). As far as I can remember there is no upper limit (other than that for positive 32 bit signed integers).

Thanks!