Vista - vista connectivity problem

Hello
I have a very strange vista (sp1) problem with internet connectivity. I have
a wifi router through which i am connecting to the Internet. This router is
also DHCP server and my computer obtains dynamic IP address perferctly. But
when I try to first contact the gateway (router) the ip address is lost at
once and an apipa address is obtrained. And this illogical event is logged
"The wait operation timed out.. Your computer will continue to try and obtain
an address on its own from the network address (DHCP) server." And it is even
when i ask DHCP for the new address. It gives me the same one (because of
cache) and the problem occures again. What is very strange is that when i
start my computer with disabled network wifi adapter and after vista is
completly started i turn it on, the problem is solved. So far, I have tried
to reinstall the tcp stack - does not help.
Please help me otherwise i will have to upgrade to winXP.