The new Minecraft Launcher that was released for Minecraft Version 1.6.1 causes a very severe frame rate drop in both Minecraft 1.5.2 and Minecraft 1.6.1 for an unknown reason. However, the previous launcher does not have this problem.

The two screenshots show a considerable difference in the game's frame rate to make it near impossible to play. (The screenshot taken during the day is from the old launcher and the screenshot taken at night is from the new launcher.)

Please note that I DO NOT have a dedicated graphics card! I have been running Minecraft off of my internal one and it has always worked up until 10:00 p.m. EST Monday 7/1/13. However, I was using the new launcher the day before the official 1.6.1 release and it did not cause my frame rate to drop once!