My hosting provided (hostgator) made me install WP Super Cache, at which point google analytics started showing zero visits for a site that is getting thousands of hits a day. Looking online I found that several people were having similar issues...not a lot, and it seems to be related to how the analytics code is being handled, but this is definitely a problem for Sentence.
So now I'm trying Total Cache.
My other solution, I guess, would be to give up Google Analytics and try another analytics plugin, see whether that might work. Any experience here with one that works well for you? I MUST have a cache plugin to avoid dedicated hosting costs for this site...so it's worth a try to avoid that expense.