Hey I noticed this when I started working on my map again and did some digging, to save me time of explaining whats going on I have exactly what this guy had,
<a href="http://community.roll20.net/discussion/1156/worse-resolution-on-maps-after-patch#Item_4" rel="nofollow">http://community.roll20.net/discussion/1156/worse-resolution-on-maps-after-patch#Item_4</a>
But it says closed and it sounds like you fixed it which makes me wonder if I just didn't get the patch or if it's back with a vengeance haha.
Edit: I just noticed that if I pull the map from the "Results from your Art Library" section then its at the resolution it should be, but when I import the map over its horrible. Still clueless.