Tachyon,

USBSERVICE is a PBP statement, not an ASM statement. So it can't be in an ASM/ENDASM block.
It must be like this ...
Code:
'----[Interrupt handler -- Service USB]--------------------------------------------------
USBServiceISR:
        USBSERVICE
@   INT_RETURN
Then add an underscore in the INT_Handler statement.
Code:
'---[Interrupts List]---
ASM
INT_LIST  macro   ;Source,   Label,          Type,  ResetFlag?
    INT_Handler   USB_INT,  _USBServiceISR,  ASM,   yes
    endm
    INT_CREATE
ENDASM
You can only have 1 USBINIT in your program.
And there should never be a USBSERVICE after the interrupt has been enabled.
Interrupting a USBSERVICE to do a USBSERVICE can cause bad things to happen.
Code:
'---[Initialize Chip]--------------------------------------------------------------------
InitChip:
	PAUSE 100
	USBINIT
	USBSERVICE
	UIE = $7F
	UEIE = $9F
;	PAUSE 500
;	USBINIT
;	USBSERVICE
	@ INT_ENABLE USB_INT
;	USBSERVICE
The following program works perfectly here on a LAB-XUSB with an 18F4550.
Code:
'***************************************************************************************
'	Title:		USB CDC and DT_INTS Testing
'	CPU:		18F4458
'   Clock:		20 MHz External Clock
'
'****************************************************************************************

ASM
	__CONFIG    _CONFIG1L, _PLLDIV_5_1L & _CPUDIV_OSC1_PLL2_1L & _USBDIV_2_1L
	__CONFIG    _CONFIG1H, _FOSC_HSPLL_HS_1H & _FCMEN_OFF_1H & _IESO_OFF_1H
;	__CONFIG    _CONFIG1H, _FOSC_ECPLLIO_EC_1H & _FCMEN_OFF_1H & _IESO_OFF_1H
	__CONFIG    _CONFIG2L, _PWRT_OFF_2L & _BOR_ON_2L & _BORV_2_2L & _VREGEN_ON_2L
	__CONFIG    _CONFIG2H, _WDT_OFF_2H & _WDTPS_512_2H
	__CONFIG    _CONFIG3H, _CCP2MX_ON_3H & _PBADEN_OFF_3H & _LPT1OSC_OFF_3H & _MCLRE_OFF_3H
	__CONFIG    _CONFIG4L, _STVREN_ON_4L & _LVP_OFF_4L & _XINST_OFF_4L & _DEBUG_OFF_4L
ENDASM


DEFINE OSC 48
DEFINE NO_CLRWDT 1
DEFINE USB_BUS_SENSE PORTD,3

INCLUDE "cdc_desc.bas"
INCLUDE "DT_INTS-18.bas"

'---[Interrupts List]---
ASM
INT_LIST  macro   ;Source,   Label,          Type,  ResetFlag?
    INT_Handler   USB_INT,  _USBServiceISR,  ASM,   yes
    endm
    INT_CREATE
ENDASM


	goto InitChip


'----[Interrupt handler -- Service USB]--------------------------------------------------
USBServiceISR:
	USBSERVICE
@	INT_RETURN



'---[Initialize Chip]--------------------------------------------------------------------
InitChip:
	PAUSE 100
	USBINIT
	USBSERVICE
	UIE = $7F
	UEIE = $9F
	@ INT_ENABLE USB_INT

	PORTA = 0
	PORTB = 0
	PORTC = 0
	PORTD = 0
	PORTE = 0

	'setup port i/o
	TRISA = %00000000
	TRISB = %11111111
	TRISC = %00110000
	TRISD = %00001000
	TRISE = %00000000

	'all dig
	ADCON1 = %00001111
	
	'enable port b pullups
	INTCON2.7 = 0

	

Main:
	goto Main


	end
Make sure you have 0.1uF bypass capacitors from VDD to VSS.
And some people say that you also need 0.1uF from the USB +5V to VSS, but I've never had to do that.