i have fixed a lot of problems by adding your suggestions.

Code:
'****************************************************************
'*  Name    : TAG NUMBER.BAS                                    *
'*  Author  : LEONARDO BILALIS                                  *
'*  Notice  : Copyright (c) 2011 [LEONARDOS BILALIS]            *
'*          : All Rights Reserved                               *
'*  Date    : 11/6/2011                                         *
'*  Version : 1.0                                               *
'*  Notes   : this program allows you to see the                *
'*          : Number of the RFID tag                            * 
'*          :                                                   *
'****************************************************************
@ __config _INTRC_OSC_NOCLKOUT & _WDT_ON & _PWRTE_ON & _MCLRE_OFF & _LVP_OFF & _CP_OFF
wsave   VAR BYTE    $20     SYSTEM      ' location for W if in bank0
;wsave   VAR BYTE    $70     SYSTEM      ' alternate save location for W 
                                         ' if using $70, comment wsave1-3

' --- IF any of these three lines cause an error ?? ------------------------
'       Comment them out to fix the problem ----
' -- Which variables are needed, depends on the Chip you are using -- 
wsave1  VAR BYTE    $A0     SYSTEM      ' location for W if in bank1
wsave2  VAR BYTE    $120    SYSTEM      ' location for W if in bank2
;wsave3  VAR BYTE    $1A0    SYSTEM      ' location for W if in bank3
Include "MODEDEFS.BAS"
INCLUDE "DT_INTS-14.bas"     ' Base Interrupt System
INCLUDE "ReEnterPBP.bas"     ' Include if using PBP interrupts
CMCON = 7
;-----------------------------------------------------------------
LED   VAR  PORTB.3
  
ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   TMR1_INT,  _ToggleLED1,   PBP,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor
ENDASM

T1CON = $31                ; Prescaler = 8, TMR1ON
@ INT_ENABLE  TMR1_INT     ; enable Timer 1 interrupts
;-----------------------------------------------------------------

DEFINE OSC 4	'Set oscillator in MHz 
DEFINE LCD_DREG PORTB  'define port to LCD
DEFINE LCD_DBIT 4      'RB4 RB5 RB6 RB7 to D4 D5 D6 D7 display
DEFINE LCD_RSREG PORTA 'RS on porta
DEFINE LCD_RSBIT 0     'RS on porta.0
DEFINE LCD_EREG PORTA  'Enable on porta
DEFINE LCD_EBIT 1      'Enable  porta.1
DEFINE LCD_BITS 4      ' 
DEFINE LCD_LINES 2     'lines 2
PAUSE 200             ' Stop 200ms
;----------------------------------
LCDOUT $FE,1           ' power lcd
Lcdout $FE,1,4
lcdout $FE, 1," Copyright 2011"
lcdout $FE, $C0,"Leonardo Bilalis"
;----------------------------------

' -----[ Variables ]-------------------------------------------------------

buf	    VAR	byte [10]' RFID bytes buffer
tagNum	VAR	Byte	 ' from EEPROM table
idx	    VAR	Byte	 ' tag byte index
char	VAR	Byte	 ' character from table

Main:
pause 500
lcdout $FE,1," Please use your"
lcdout $FE, $C0,"Personal RFIDTAG"
pause 500
SERIN2 portb.1, 84, [WAIT($02),Str buf\10]
pause 1000
LCDout $fe,1, "TAG ID:"
lcdout $fe,$C0, "NO: ", str buf\10
pause 5000
goto main

'---[TMR1 - interrupt handler]--------------------------------------------------
ToggleLED1:
TOGGLE led
@ INT_RETURN
now i only get the following

error [118] overwriting previous address contents [2007]