I don't bump my posts, but I don't want this to drop off of the front page. Is there no one who has dealt with this issue and can help me solve it?
--------------- Added [DATE]1338266441[/DATE] at [TIME]1338266441[/TIME] ---------------
Okay, so I had to do it the old fashioned way -- solve it myself.
The problem was one of permissions on the store_sitemap directory. I sudo chmod 777 on it, then in the ACP > XML Sitemap > Sitemap File Path I put in "store_sitemap" (without the quotes) and clicked on Save. No errors this time.