The same thing is happening to me as was mentioned in the first post on this topic. I have identified the problem: The java.exe process is constantly increasing the amount of RAM being used as time goes on, until it's used up all the memory and the game gets very laggy before crashing and telling you that minecraft has run out of memory. In addition to this the .exe laucher is failing to work and just says "checking Launcher version" then closes, so i'm having to use the .jar application.
Ive been looking around and there seem to be quite a few people who also share this problem, i've seen youtube videos, forum discussions ect. But the only feedback is from others who are complaining of the same problem. There has so far been NO solutions! Please get back to me on this someone and tell me how I fix this!