Using Wifi in Starbucks on a Mac?

This isn't the most scintillating post I've ever written, but I hope it helps someone else one day, as it took me a while to figure it out.

I'm running Snow Leopard on my lovely MacBook Air, and up-to-date with all the latest system updates.  And I've been treating Starbucks pretty much as my office whenever I'm in town, ever since they introduced free wifi for Starbucks card holders.  But today I couldn't get on the network. 

Turned out I had a couple of DNS entries, and deleting them solved the problem.  (To get rid of them, go to Network in System Preferences, hit Advanced, then delete them from the left-hand side of the DNS tab.) 

I can't say with absolute certainty that I didn't add those DNS entries myself, though I have no recollection of ever doing so.  My suspicion is that something "helpfully" created them for me - possibly something I've added (or upgraded) in the last few weeks since I was last connected in Starbucks? 

Anyway, problem fixed (until I find there's some network I use where those DNS entries were important...)