Comment 71 for bug 24776

A similar problem still occurs August 2014 on Lubuntu 14.04.1:

I can't connect to my dd-wrt router running an (older WEP secured) mixed-NG access point.

As with some of the above solutions, switching my router from NG-mixed to BG-mixed solves the problem, allowing me to connect to my router using the problematic wireless interface, but I have some newer devices that can't connect to BG-mixed access points so I'd like to make changes on the device side rather than on the router side.

I've also tried the NDISWrapper solution using the inf files here: https://downloadcenter.intel.com/SearchResult.aspx?lang=eng&ProdId=944 (and I made sure ipw2100 isn't loaded and ndiswrapper is). The device works like the native linux driver, but the problem remains.

I should note the linux-firmware package in the Ubuntu repository contains the latest firmware, which is good given the official host http://ipw2100.sourceforge.net/firmware.php has a dead link for the download.

It's unfortunate that this bug is still unsolved after nearly 10 years. My HP Pavilion zt3000 is an amazing laptop even in 2014 and still has many more years of life ahead of it. So my long-term solution is to use a small, low-cost USB "nano" wifi adapter and ignore the internal interface. Not ideal, but it gets the job done.