Hi,
At about line 30 in file netcdf4_constants.f90, the following code:
integer (kind = EightByteInt),  parameter, public :: &
     nf90_fill_uint   = 4294967295_8
should be changed to read:
integer (kind = EightByteInt),  parameter, public :: &
     nf90_fill_uint   = 4294967295_EightByteInt
This is needed because the NAG compiler does not, by default, use the 
typical practice of using byte counts for kinds.  An 8-byte integer 
actually has a kind of 4.  (Kinds are 1, 2, 3, and 4 for one-byte, 
two-byte, four-byte, and eight-byte integers.  Kind=8 is not accepted.)
NAG does have a -kind=byte compilation option.  But use of this option 
introduces further problems.  Namely that all Fortran code that USEs a 
module compiled in this mode must also be compiled the same way.  Which 
is a pain for large programs that use libraries from multiple sources.
I checked the netcdf-fortran-4.4-beta1 tarball, and the bug is not 
fixed.  The same code appears in file netcdf_constants.f90 at around 
line 152.
Walter