adding variables in netcdf4 fortran 77

Question

I'm trying to save the outputs of a model (written in fortran 77) in netCDF4 format. I'm using gfortran. Since I'm a fresher in fortran, I wrote a simple code in which I create dummy variables and add it to my test netcdf file emulating dimensions,variables and attributes of the model. It works perfectly.

I proceeded to the next step knowing that my code works. Well, the thing is that the very same code does not work and I cannot find out why. The model code is old and "organized" in one single .for file. Interestingly enough, the main code was written as a subroutine. The basic structure of the program is:

  implicit real*8(a-h,o-z) 
  character dummy*80
  ...
  call main(delt,npl)      
  end    

  subroutine main(delt, npl)
  *variable declarations*
  ...
  end

My approach was to create the netcdf file outside the "main" subroutine. It works and the netcdf file was created. Inside "main" I define dimensions and variable (since they're based on the data generated inside the subroutine). The code works like a charm when I add only the dimensions:

  Setting dimensions
  nc_status = nf_def_dim(ncid,'parcel_id', ntot, prcl_dimid)
  if (nc_status .ne. nf_noerr) call handle_err(nc_status)
  nc_status = nf_def_dim(ncid, 'time', icomp, time_dimid)
  if (nc_status .ne. nf_noerr) call handle_err(nc_status)
  End define mode.
  nc_status = nf_enddef(ncid)
  if (nc_status .ne. nf_noerr) call handle_err(nc_status)
  Close the file
  nc_status = nf_close(ncid)
  if (nc_status .ne. nf_noerr) call handle_err(nc_status)

The nc file generated has the right dimensions with the right size. The problem comes when I try to add the variables:

  Dimensions
  nc_status = nf_def_dim(ncid,'parcel_id', ntot, prcl_dimid)
  if (nc_status .ne. nf_noerr) call handle_err(nc_status)
  nc_status = nf_def_dim(ncid, 'time', icomp, time_dimid)
  if (nc_status .ne. nf_noerr) call handle_err(nc_status)
  dimids(1) = prcl_dimid
  dimids(2) = time_dimid

  Variables
  **nc_status = nf_def_var(ncid, 'latitude', NF_FLOAT, 2, dimids, 
 +     lat_varid)**
  if (nc_status .ne. nf_noerr) call handle_err(nc_status)

  End define mode.
  nc_status = nf_enddef(ncid)
  if (nc_status .ne. nf_noerr) call handle_err(nc_status)

  Close the file
  nc_status = nf_close(ncid)
  if (nc_status .ne. nf_noerr) call handle_err(nc_status)

I get the following error from the bold-font part of the code.

Error: NetCDF: Not a valid data type or _FillValue type mismatch

First, this code (exactly like that) works when I create my simple fortran file with dummy values. Second, no fillvalue was defined by me. And third, NF_FLOAT is a valid data type according to UNIDATA website.

I've also tried to create the whole netcdf4 inside the "main" subroutine but I get the same error. I've used all my imagination trying to figure out what is happening and, apparently, no one else had the same problem (or at least did not mention it online...). But I'm a beginner in fortran and everything is possible.

All the best and sorry if it is a stupid question for you. It hasnt been stupid for me at all!