RSS Full Text Syndication reverts

I’m trying to assist someone with their WordPress installation. they’re syndication feeds are showing up truncated. I’ve gone to Options > Reading, and under “Syndication Feeds >For each article show…” the “summary” radio button is chosen. However, when I select “full text” and then save the options, it immediately reverts to Summary – it doesn’t seem to accept the change.

Anyone have any idea as to why this is?

EDIT: Another one in WP 2.0.5 is also doing the same thing – will not take the “full text” change and reverts to “summary”.