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Devin,
During a capture I saw that the Association Request frame set off protection, but that wouldn't explain one AP causing another AP to go into protection.

Here are the results from my test, per your scenarios.

1 - 802.11b STA Associated to Linksys AP in mixed mode

Beacon:
.... .1.. Barker Preamble Mode
.... ..0. Disable Use of Protection
.... ...1 Non-ERP Present

2. 802.11b AP (Cisco 1200 with all 11g data rates disabled)

Linksys Beacon:

.... .1.. Barker Preamble Mode
.... ..0. Disable Use of Protection
.... ...1 Non-ERP Present

3. 802.11b AP (Cisco 1200 with all 11g data rates disabled) and Orinoco 11b card associated with the Cisco 1200.

Here is the beacon from the Cisco


.... .1.. Barker Preamble Mode
.... ..1. Use Protection
.... ...1 Non-ERP Present

Here is the beacon from the Linksys

.... .1.. Barker Preamble Mode
.... ..0. Disable Use of Protection
.... ...1 Non-ERP Present


It sure does look like Linksys completely disabled protection. Like I said originally, I think that it could provide for better throughput if protection doesn't get enabled when an 11b STA is associated. The kicker to the whole thing is how much talking the 11b STA is doing. Too much without protection and the collision rate goes way up. If the 11b STA is talking very little and the AP is in protection, throughput will be diminished unnecessarily.

Its a tough one, but I say that enterprise level equipment should have a configurable feature to allow 11b STA's to associate, but don't go into protection. Imagine you get a few guests into your network and you don't know what type of card they will have. It would be great to allow 11b to associate, but don't bring down the entire network's throughput with unnecessary CTS frames. Again, in this situation I believe that the solution is worse than the problem.