It shows that icon when another WiFi device is offering you a connection in Ad-Hoc mode (peer to peer WiFi), as opposed to Master mode which base stations offer.

My house doesn't have WiFi, so I use this mode when my laptop is on wired ethernet, so that my laptop can provide WiFi internet access to the N900

So most likely you are seeing this icon because of a device in the vicinity, not because of any software updates.