Hi Bo61,
We are really pleased that you like the plugin and am sorry that your experience was not perfect.
I also discovered this problem when trying to add the Twitter follow button to the plugin, as the Twitter javascript file then takes over our Favorite, Re-Tweet and Reply buttons opening a second window (if you are logged into Twitter with that browser).
I will do some checks to make sure it is not us causing this, I removed the follow button feature until I can prevent this occuring. Could it be that another plugin has added the Twitter javascript file, which is then also creating a popup for our buttons?
Either way, I am working to prevent this happening, whether it is us who add the file or not. Thanks for letting us know this was a problem for you, it will be addressed.