Yes! 
After adding these lines in kernel config:

option PCIBIOS_BUS_FIXUP  (Thanks David Brownlee)
option PCIBIOS_ADDR_FIXUP

i got the Xircom RBEM56G-100 (CARDBUS) to work. YIPPI !!!

So now I'm pleased with my situation :) Thank you all!

-------

I also tested the following cards on my cardbus-ENABLED kernel:

ifconfig	Card name				STATUS
--------------------------------------------------------------
(awi)		Netwave AirSurfer Plus (pcmcia):       	Works
(ep)  		3Com 3C589C Etherlink III (pcmcia):    	Works
(ep)  		3Com 3CCE589EC Megahertz (pcmcia):     	Works
(tlp) 		Xircom RealPort RBEM56G-100 (cardbus): 	Works (Modem not tested)
(tlp) 		Xircom CBEM56G-100:                    	Works (Modem not tested)

Xircom Creditcard Netwave (pcmcia): 
(cnw) Freeses the machine. Works great when running on cardbus-DISABLED
kernel.

Xircom RealPort REM56G-100 (pcmcia): (Modem not tested)
Does'n work. Nothing running 'ifconfig'. Here is the message from
/var/log/messages:

<CUT>
Jul 19 12:55:48 ob3000 /netbsd: pcmcia0: CIS version PC Card Standard 5.0
Jul 19 12:55:48 ob3000 /netbsd: pcmcia0: CIS info: Xircom, CreditCard
Ethernet 10/100 + Modem 56, CEM56, 1.00
Jul 19 12:55:48 ob3000 /netbsd: pcmcia0: Manufacturer code 0x105, product
0x110a
Jul 19 12:55:48 ob3000 /netbsd: pcmcia0: function 0: network adapter, ccr
addr ff80 mask 67
Jul 19 12:55:48 ob3000 /netbsd: pcmcia0: function 0, config table entry
39: I/O card; irq mask 8ebc; iomask a, i
ospace 2e8-2ef; mwait_required rdybsy_active io8 io16 irqshare irqpulse
irqlevel powerdown
Jul 19 12:55:48 ob3000 /netbsd: pcmcia0: function 0, config table entry
31: I/O card; irq mask 8ebc; iomask a, i
ospace 3e8-3ef; mwait_required rdybsy_active io8 io16 irqshare irqpulse
irqlevel powerdown
Jul 19 12:55:48 ob3000 /netbsd: pcmcia0: function 0, config table entry
23: I/O card; irq mask 8ebc; iomask a, i
ospace 2f8-2ff; mwait_required rdybsy_active io8 io16 irqshare irqpulse
irqlevel powerdown
Jul 19 12:55:48 ob3000 /netbsd: pcmcia0: function 0, config table entry
15: I/O card; irq mask 8ebc; iomask a, i
ospace 3f8-3ff; mwait_required rdybsy_active io8 io16 irqshare irqpulse
irqlevel powerdown
Jul 19 12:55:48 ob3000 /netbsd: pcmcia0: function 0, config table entry
63: I/O card; irq mask 8ebc; iomask 3, i
ospace 0-7; mwait_required rdybsy_active io8 io16 irqshare irqpulse
irqlevel powerdown
Jul 19 12:55:48 ob3000 /netbsd: com1 at pcmcia0 function 0: serial device
Jul 19 12:55:48 ob3000 /netbsd: com1: ns16550a, working fifo
</CUT>