"..negative longitude values between 0 and -1 seem to get parsed as their absolute values.."
I guess I'll have to blame jcwren for that one :p
If you have a look at the values on the MonkMap page (which is where I got the data from), you'll see that your longitude is given as 0.556111 (positive). Even though it's definitely entered as a negative value on your homenode.
/me looks at jcwren... ;)
Update (2006-07-04): I managed to speak to jcwren this morning, and he has fixed this problem. Apparently it was something to do with the way that perl handles a "negative 0" value.