I switched hosting plans this morning and switched to a different server where I get more storage and memory usage. My site is rather slow due to many requests to the database, and I am working on a better site. The speed of my site increased drastically after the switch. On the flip side, I am currently having my best day in nearly 2 months for my Adsense CTR. It has been dropping every month, and today my CTR is close to being double the average. I am curious to see how my general user stats are over the next few days for visitors.
If your site is very slow and it takes 3 seconds or more to load you lose 50% of your visitors. Maybe getting a better hostingplan you increased your visitors and also they might stay longer and have a bigger chanse to click the ads.
I think its just due to its taking too much time to load in your site plus may be some auto visitors at your old server
I once read an interesting theory in Webmasterworld that your CTR will go up when your server is too slow. The reason attributed was that the visitors get bored of the slow server and try to leave your site by clicking ads. My guess is that your case can also be related to this theory. Can you report in due course here if this theory holds good for you?
I will share my results after the weekend is over. As of now, my CTR since the change is about .5% higher than the average of the last 30 days. Not a lot, but it adds up when you have a lot of page displays. I'm more curious about my visitor stats, which will take a few days for me to record and compare.