I use Google Chrome (latest version), and pretty much any image with transparency gets affected, like this one for example
When i click 'Open image in a new tab' and then click 'Copy image' on it and paste it into PDN, it becomes this
I went back to version 4.1.6 to see if it was just an issue with the beta, and when i did, pasting that same image into PDN worked just fine
On another note; If i copy an image i already have open in PDN that has transparency, and paste that either as a new layer or a new file, it'll keep it's transparency, so it just seems to be an issue with copying image data from outside sources, such as a web browser
Also, saving a transparent image from my browser and then opening it in PDN keeps the transparency, so it's only to do with copying the image