As far as I know N900's internal wireless LAN is a directional type antenna. Whilst it does not definitely mean that it cannot sense packets from other directions, it is virtually weaker to detect packets from other directions than where the antenna is normally facing.

If I am not mistaken the wireless module is close to the bluetooth module on the N900's PCB which is on the obverse side (where the screen and keyboard is, but on the screen part of the device its in the body of course). So maybe if you move closer to the wireless router for example you maybe able to get broadcast/multicast packets found from your N900.

The other things you might want to have a look at (not that you haven't but I guess its still worth mentioning) is:

• Wireless transmit power is set the maximum (which is 100mW), if not try turning it onto maximum.
• Disable power saving mode, I personally find power saving mode a bit of a pain to work with when half the time I SSH into the device and seeing the device at times takes a few seconds to respond.
• Bluetooth module disabled. This one is probably the most critical point as bluetooth shares the same radio spectrum as 802.11b/g which is exactly what N900 communicates on wireless networks. Bluetooth co-existance may sometimes help with not having to disable bluetooth completely however its also noteworthy to first disable bluetooth just in case it hinders the wireless chipset from sensing wireless packets.

Other than that I am somewhat really stumped, it is probably possible in theory that if for instance you are testing this on a different wireless router and the wireless router has a completely different setup which may change the outcome of the scenario.