Intel Fortran says actual argument doesn't match dummy argument?

Apologies in advance for what seems to be a very basic question. I'm not a Fortran programmer, unfortunately, but I'm in a position of having to maintain some legacy FORTRAN77 code, and it is not compiling in Intel Visual Fortran Parallel XE 2013 (with VS2010) on Windows7.

The error I'm getting is 

> error #6633: The type of the actual argument differs from the type of the dummy argument.

It occurs in several calls to subroutines that are defined within the project. This code has the statement 

IMPLICIT REAL(8) (A-H,O-Z)

throughout, in both the calling function and the called subroutine. (It had been `REAL*8`, but I changed it.)

Doesn't that mean that the arguments, all of which have names that fall into the range (A-H,O-Z), will be two-byte reals? I don't know where they are being declared or otherwise converted to any other type. The only functions called within the subroutines are intrinsic math functions, such as cos, sin, atan2. 

Below is an example (I left out an INCLUDE statement that included a file with the IMPLICIT REAL statement above as its first line):

C    Transform from RS to RL
    call RS$RL(0,iobl,1,vrel,xlatgc,gam,az,vph,vth,vr,
*                 xlatgd,gaml,azl,vphl,vthl,vrl)

which calls

      SUBROUTINE RS$RL(ID,IOBL,IV,VREL,TH,GAM,AZ,VPH,VTH,VR,
     *                 THL,GAML,AZL,VPHL,VTHL,VRL)

C*  DECLARATIONS
      IMPLICIT REAL(8) (A-H,O-Z)
C     IMPLICIT REAL*8(A-H,O-Z)
      DEL = THL-TH
      IF(ID.EQ.0) THEN
C*  TRANSFORM FROM RS TO RL FRAME
        IF(IV.EQ.0) THEN
             VPH  = VREL*COS(GAM)*SIN(AZ)
             VTH  = VREL*COS(GAM)*COS(AZ)
             VR   = VREL*SIN(GAM)
        ENDIF
        IF(IOBL.EQ.0) THEN
             VPHL = VPH
             VTHL = VTH
             VRL  = VR
        ELSE
             VPHL = VPH
             VTHL = VTH*COS(DEL)-VR*SIN(DEL)
             VRL  = VTH*SIN(DEL)+VR*COS(DEL)
        ENDIF
        GAML = ATAN2(VRL,SQRT(VPHL**2+VTHL**2))
        AZL  = ATAN2(VPHL,VTHL)
      ELSE
C*  TRANSFORM FROM RL FRAME TO RS FRAME
        IF(IV.EQ.0) THEN
             VPHL = VREL*COS(GAML)*SIN(AZL)
             VTHL = VREL*COS(GAML)*COS(AZL)
             VRL  = VREL*SIN(GAML)
        ENDIF
        IF(IOBL.EQ.0) THEN
           VPH  = VPHL
           VTH  = VTHL
           VR   = VRL
        ELSE
           VPH  = VPHL
           VTH  = VTHL*COS(DEL)+VRL*SIN(DEL)
           VR   =-VTHL*SIN(DEL)+VRL*COS(DEL)
        ENDIF
        GAM  = ATAN2(VR,SQRT(VPH**2+VTH**2))
        AZ   = ATAN2(VPH,VTH)
      ENDIF
      RETURN
      END

The error messages complain about the arguments, vrel, xlatgc, gam, az.

Any suggestions or clues are much appreciated.