Something is wrong with the launcher *strong* Not a big issue but boy does it bug me.

When i minimize the minecraft launcher before logging in and bring it back up again after 30 mins it shows this black square that keeps scrolling down from the top right corner of the launcher down and down and then restarts on the line next to it. i don't know if this is a bug with the launcher or its just my PC but i need Jens (Jeb_) or Dinnerbone (Nathan Adams) to solve this issue, please check the coding in the launcher if you find this bug. Thank You!