I am regularly getting the above error when I try to print out Purchase Orders in T6 saying that "You have tried to access a file that has not been previously opened, or the file number value (FNUM) passed was o.
 
Has anyone else experience this?  
 
The PO line is also not being saved all the time..... once you have entered through the line it won't go to another but instead goes back to line 1.