What does this error mean??

Anyone know, its attached.

My guess is you are using 2.5, and you do not have a range in your priority field for the sitemap because you copied briansol's old guide for the sitemap.

Is this correct? If so, make the priority a range.

yes, correct. What section is that changed in, and what ranges should I use?

Well, if you like the settings from briansol, you can make the range start a bit smaller, and go past it a bit, so it keeps it all in the same area.

All sections that have priority now have a range. This was added to prevent the warning from Google saying all URLs have same priority.