I have been puzzled by unstable connection with my new Mac Book. Earlier one did not have problem but new one had lots of problem - I had my AirPort (Wi-Fi/Wireless) connection dropping every 5 minutes. I suspected VMWare fusion because I was getting messages in system logs where VMNet interfaces were having some problems. I went through vmware forums and figured out that it might be a problem with VMWare. After being 100% sure that its vmware, I just uninstalled vmware. Now I did not have any VMNet interfaces but my machine was still dropping connection with my DSL wireless router (in my case its 2Wire).
After going through logs and everything else.. I came across this (Apple forum) link. And then I changed channel, frequency, encryption and what not.. but no luck. The only solution which is also given in this thread is.. keep pinging the router from terminal and link never drops!
I can not belive... but the solution is - Keep pinging gateway continuously.