it is a bug, although admins in bugzilla refuse to accept it as such. The N900 user interface is lacking an option to choose NOT to enter into WIFI Protected Setup when encountering a router that

The workaround is to manually configure the connection from the phone settings menu. This is, of course, quite counterintuitive, and had me thwarted for a week (nearly sent my phone back for a refund).

Not fixing such a simple UI bug and therefore making people unable to connect to a rapitdly increasing number of public wifi hotspots is sure-fire way to have your customers running back to Apple with their arms wide open.