Which is more likely?

I keep a running total of my calories eaten and calories burned.  According to my calculations, I should have lost 2.35 lbs over the last 20 days.  My weight has not changed (I've weighed a few times to account for water weight, etc..). 

Which is more likely?   Am I somehow underestimating how much I eat, or is CC overestimating my calories burned?  How do I figure out what to adjust to achieve a weight change? Any ideas?

First, keep in mind that although so many calories = so many pounds loss - the body ain't a machine, and it isn't going to act like one.  Sometimes, our body's seem to wait a while, hold on to the weight, and then drop 2 pounds over night.

I would maintain the exercise level you are doing, and try dropping my calories just a bit, say 150 a day, for a couple of weeks to see if that helps.

Oh, and if you aren't routinely using a food scale, get an inexpensive digital one and use it for EVERYTHING for a week or two.

If you aren't using a food scale and accurately recording everything you eat, then underestimating is quite likely.  It's also very likely CC is overestimating your calories burned.  I use a heart rate monitor and compare the reading to CC sometimes, and my HRM is always less than what CC says.

Could be either, but overestimating calories burned is more common. Calculating calorie intake is much simpler, especially if you're measuring portions. 200 calories is 200 calories; okay, it might be 190 or 210, but you're not going to be wildly off. But so many factors go into calorie expenditure that it's more difficult to get an accurate count.

just keep being healthy, and your body will balance out.

forget the scale, use your clothes as a measure of weight loss.

people eat healthy for a few days or a couple of weeks and think they are automatically the healthiest person in the world [i am not talking about you specifically] but i know this is how i always felt when i began my weight loss.

i eat like vegetables all day and get on the scale and assume it's all just gonna drop off. there are a lot of factors that keep your scale from being an accurate measure of weight loss. don't let it discourage you. if you know you are doing the right thing, then just keep doing it.

From your profile it looks like you've already successfully lost 30+ pounds and that's really great. It sounds to me like your body is resisting going past a certain happy weight. To go further would require much more drastic exercising, IMHO. You may want to consider deeply if this is what you want.