compil usb PIC18F2450 problem

Hi
it is the first time that i work with USB
i use PIC18F2450
I download some code for testing
and the compiler give me error:
Error[113] c:\pbp2~1.6\pbppi18l.lib 724 : Symbol not previously defined (USBDeviceTasks)
Error[113] c:\pbp2~1.6\pbppi18l.lib 723 : Symbol not previously defined (PutUSB)
Error[113] c:\pbp2~1.6\pbppi18l.lib 724 : Symbol not previously defined (PutUSB)
Error[113] c:\pbp2~1.6\pbppi18l.lib 723 : Symbol not previously defined (GetUSB)
Error[113] c:\pbp2~1.6\pbppi18l.lib 724 : Symbol not previously defined (GetUSB)
Error[113] c:\pbp2~1.6\pbppi18l.lib 724 : Symbol not previously defined (USBDeviceTasks)
Error[113] c:\pbp2~1.6\pbppi18l.lib 723 : Symbol not previously defined (PutUSB)
Error[113] c:\pbp2~1.6\pbppi18l.lib 724 : Symbol not previously defined (PutUSB)
Error[113] c:\pbp2~1.6\pbppi18l.lib 723 : Symbol not previously defined (GetUSB)
Error[113] c:\pbp2~1.6\pbppi18l.lib 724 : Symbol not previously defined (GetUSB)

and more
what is the problem ?

Thanks
Eyal