This has happened several times, but I've just realized that this weird "Oops sorry!" message seems to be causing it.
Here is the most recent case I'm facing with Hawken. I tried adding the game to my Wishlist, but failed. It displayed the message "Oops sorry!" for a moment. I refreshed the page, and the button disappeared.
I checked my Wishlist page, just in case it's been there. But unfortunately the game has not been added to my Wishlist either.
This has happened several times and it's quite annoying.
Anyone can help me?