Page Keywords -- Why do they disappear when I save the settings?

I've been trying to use SmartCrawl lately and either I'm missing something or I'm having a problem. Whenever I type keywords into the space for Page Keywords (on the Title & Meta page) they disappear as soon as I save the settings. Is that supposed to happen? I've looked for them in the page source code but don't find them there, either.

This has happened with both sites that I've been trying to get the SEO set up ( and