charmm IO error

 I generated a equil1.trj file and wanted to extract some information from
 it.  But I got the following error.
 eor/uio: [1010] off end of record
 logical unit 11, named 'equil1.trj'
 lately: reading sequential unformatted external IO
 My input file is:
 ! Convert the files
 open unit 11 read file name equil1.trj
 open unit 1 write file name equil1A_1.dcd
 merge coor firstu 11 nunit 1 skip 1 outputu 1
 begin 21000 stop 25000 sele segid A .and. resid 1:180 end
 Anyone knows what that error means?  My trajectory file is about 6MB
 large.  When I ran the simulation, the energy file was written out okay
 and the output of charmm said normal termination.