Same problem here. I tested with the qa-xml-sitemap.php and the values for $hotstats['base'] is 11350316032 and for $hotstats['spread'] is 143163392. Shouldn't "base" be the smallest value? Some of the priority values are <0.
Some of the "hotness" values in the database are quite huge, like for example 1.13748e+10.
Maybe the problem can be prevented by applying round(x,1)?