Comment 3 for bug 110187

Further information & work around:

I have discovered that Network Manager writes the WEP passphrase to /etc/network/interfaces as plain text despite selecting Hex. I can get my network working with static IP iff I manually change /etc/network/interfaces and enter my WEP passphrase in Hex. The result of this intervention is the I can get wireless working with static IP but nm-applet no longer does its job and the routing table comes up misconfigured(ie. sends internal traffic to eth0 instead of wlan0. I assume nm adjusts this normally but my intervention stops this being properly configured at the time the network is being brought up). To have the routing table come up in a working form I have had to remove all references to eth0 in /etc/network/interfaces.

Also note: I now think that avahi error was a symptom & not the cause as I get no error message from avahi now. But also note that avahi enters items in the routing table which are irrelevant to my network - not sure if this is a bug or not???
I think avahi is entering this line in routing table:
169.254.0.0 * 255.255.0.0 U 1000 0 0 wlan0

Also note: The above mentioned desktop slowdown is very real when I have no network connection (a common situation with a laptop). The effect is immediate once the network is lost.