For the record this is an Intel PRO/Wireless 2915ABG Calexico2 although I don't think the problem is hardware/driver specific.
Most of the time after I suspend, resume the machine, and especially if still at the same location, the net applet network icon at the panel momentarily shows network down, then comes back and shows the green signal strength icon (and the network is connected and works.)
Sometimes the network disconnected remains, and indeed the wifi is not connected. If at that point I run drakroam (right click network icon, select wireless networks, click manage network wireless networks), it show the available networks and _shows_ my network as connected.
So there's a discrepancy somewhere between net applet and drakroam. I tried to click disconnect, then reconnect, however, it does not help.
The only remedy is restarting the machine. Upon restart it immediately connects with any further action.
I think there probably is some service or process that needs to be stopped on suspend, started on resume to fix this problem. The question is why does it sometimes work?
One possibility is DHCP. My hypothesis is that if the DHCP lease still is valid upon resume then it works. Otherwise it fails to renew it. Does that make sense, and if so, how would I fix it?