I just verified the method here and it works just fine, with 128 values.
Here's the code I used:
Code:
i       VAR BYTE
j       VAR BYTE
Array   VAR BYTE[128]

PAUSE 3000

Main:
  GOSUB ClearArray

  HSEROUT["Enter new values...", 13]
  
  For i = 0 to 127
      HSERIN[WAIT ("a"), HEX2 Array[i]]
  NEXT
  
  ' Send values back, the Array[i-1] and i//16 stuff is just there
  ' to format the output a little better, for readabillity.
  For i = 1 to 128
    HSEROUT[HEX2 Array[i-1]]
    IF i // 16 = 0 THEN
        HSEROUT[13]
    ELSE
        HSEROUT[","]
    ENDIF
  NEXT
    
    HSEROUT[13, "DONE", 13]
  
  Goto Main


ClearArray:
    For i = 0 to 127
        Array[i] = 0
    NEXT
RETURN
And here's the result:

Name: HEX string.jpg Views: 1595 Size: 89.0 KB

Now, this was on a 18F25K20 running at 64MHz, which is 16 times faster than 4MHz. On the other hand I used 115200 baud which is 12 times faster than 9600. If it refuses to work at your end then, as a test, decrease the baudrate or increase the oscillator speed.

/Henrik.