Vista - loosing connection with Dlink router ?!

Hi,

I upgraded windows XP on my laptop to Windows Vista Ultimate. All went
fine and i'm very happy with it except for one thing: sometimes when
i boot my laptop, i don't receive an IP address from the Dlink switch/
dhcp/adsl router.
I thought the DI-624 was failing and bought a brand new DI-724...
guess what: same problem again! I also changed the network cables and
the provider checked the ADSL line and it was fine. Another XP pc on
the same home network also looses connection with the router! Before
Vista, i never had this problem so it seems that Vista is causing the
router to fail somehow....? I send an email to Dlink about this
problem but no reply.....

Any ideas?

Thanks!
Kris