I'm having a similar problem. The sparkline was working fine up to a
couple of days ago, but the last two posts of mine have been showing 0
for pageviews, exits, and uniques (even though I've gotten comments on
the posts, so I know they're getting hits).. It doesn't look like the
numbers on any of my other posts have changed, either.
The rest of the dashboard analytics appear to be working fine. I'm
seeing referrers, top posts and pages, etc - that part looks
completely normal. I'm also seeing my new posts show up in the top
posts and pages section, even though its showing 0's for pageviews for
the sparklines.